Convert.ToBoolean メソッドとは何？わかりやすく解説 Weblio辞書

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.NET Framework クラスライブラリリファレンス

索引トップ用語の索引ランキング

Convert.ToBoolean メソッド (UInt16)

指定した 16 ビット符号なし整数の値を等価のブール値に変換します。

このメソッドは、CLS に準拠していません。

名前空間: System
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

<CLSCompliantAttribute(False)> _
Public Shared Function ToBoolean
 ( _
    value As UShort _
) As Boolean

Visual Basic (使用法)

Dim value As UShort
Dim returnValue As Boolean

returnValue = Convert.ToBoolean(value)

[CLSCompliantAttribute(false)] 
public static bool ToBoolean
 (
    ushort value
)

C++

[CLSCompliantAttribute(false)] 
public:
static bool ToBoolean (
    unsigned short value
)

/** @attribute CLSCompliantAttribute(false) */ 
public static boolean ToBoolean (
    UInt16 value
)

JScript

CLSCompliantAttribute(false) 
public static function ToBoolean
 (
    value : ushort
) : boolean

パラメータ

value: 16 ビット符号なし整数。

戻り値
value が 0 以外の場合は true。0 の場合は false。

プラットフォーム

バージョン情報

.NET Framework
サポート対象 : 2.0、1.1、1.0
.NET Compact Framework
サポート対象 : 2.0、1.0

参照

関連項目
Convert クラス
Convert メンバ
System 名前空間
UInt16

Convert.ToBoolean メソッド (Char)

このメソッドを呼び出すと、必ず InvalidCastException がスローされます。

名前空間: System
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

Public Shared Function ToBoolean
 ( _
    value As Char _
) As Boolean

Visual Basic (使用法)

Dim value As Char
Dim returnValue As Boolean

returnValue = Convert.ToBoolean(value)

public static bool ToBoolean
 (
    char value
)

C++

public:
static bool ToBoolean (
    wchar_t value
)

public static boolean ToBoolean (
    char value
)

JScript

public static function ToBoolean
 (
    value : char
) : boolean

パラメータ

value: Unicode 文字。

戻り値
この変換はサポートされていません。値は返されません。

例外

例外の種類	条件
InvalidCastException	この変換はサポートされていません。

解説

このメソッドは、今後使用するために予約されています。

プラットフォーム

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

開発プラットフォームの中には、.NET Framework によってサポートされていないバージョンがあります。サポートされているバージョンについては、「システム要件」を参照してください。

バージョン情報

.NET Framework
サポート対象 : 2.0、1.1、1.0
.NET Compact Framework
サポート対象 : 2.0、1.0

参照

Convert.ToBoolean メソッド (Int32)

指定した 32 ビット符号付き整数の値を等価の Boolean 値に変換します。

名前空間: System
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

Public Shared Function ToBoolean
 ( _
    value As Integer _
) As Boolean

Visual Basic (使用法)

Dim value As Integer
Dim returnValue As Boolean

returnValue = Convert.ToBoolean(value)

public static bool ToBoolean
 (
    int value
)

C++

public:
static bool ToBoolean (
    int value
)

public static boolean ToBoolean (
    int value
)

JScript

public static function ToBoolean
 (
    value : int
) : boolean

パラメータ

value: 32 ビット符号付き整数。

戻り値
value が 0 以外の場合は true。0 の場合は false。

プラットフォーム

バージョン情報

.NET Framework
サポート対象 : 2.0、1.1、1.0
.NET Compact Framework
サポート対象 : 2.0、1.0

参照

関連項目
Convert クラス
Convert メンバ
System 名前空間
Int32

Convert.ToBoolean メソッド

オーバーロードの一覧

名前	説明
Convert.ToBoolean (Double)
Convert.ToBoolean (Object)
Convert.ToBoolean (Object, Boolean)

参照

Convert.ToBoolean メソッド (Object, IFormatProvider)

指定したカルチャに固有の書式情報を使用して、指定した Object の値を等価のブール値に変換します。

名前空間: System
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

Public Shared Function ToBoolean
 ( _
    value As Object, _
    provider As IFormatProvider _
) As Boolean

Visual Basic (使用法)

Dim value As Object
Dim provider As IFormatProvider
Dim returnValue As Boolean

returnValue = Convert.ToBoolean(value, provider)

public static bool ToBoolean
 (
    Object value,
    IFormatProvider provider
)

C++

public:
static bool ToBoolean (
    Object^ value, 
    IFormatProvider^ provider
)

public static boolean ToBoolean (
    Object value, 
    IFormatProvider provider
)

JScript

public static function ToBoolean
 (
    value : Object, 
    provider : IFormatProvider
) : boolean

パラメータ

value: IConvertible インターフェイスを実装する Object か、または null 参照 (Visual Basic では Nothing)。

provider: カルチャに固有の書式情報を提供する IFormatProvider インターフェイス実装。

戻り値
value が null 参照 (Visual Basic では Nothing) に等しい場合は false。または true または false。これは、基になる型の value に対して ToBoolean メソッドを実行した結果を示します。

例外

例外の種類	条件
InvalidCastException	value が IConvertible インターフェイスを実装していません。

解説

provider を使用すると、value の内容について、カルチャに固有の変換情報を指定できます。たとえば、value が数値を表す String の場合、provider によって、その数値の表記方法に関するカルチャに固有の情報を提供できます。

基本型では provider は無視されますが、value が IConvertible インターフェイスを実装するユーザー定義型の場合は有効となります。

使用例

IConvertible を実装するクラスと IFormatProvider を実装するクラスを定義するコード例を次に示します。IConvertible を実装するクラスのオブジェクトは、Double 値の配列を保持します。各クラスのオブジェクトは ToBoolean メソッドに渡されます。このメソッドは、破棄されない配列値のいずれも 0 以外である場合に true を返します。IFormatProvider オブジェクトは、この計算で要素を破棄する方法を決定します。

Visual Basic

' Example of the Convert.ToXXX( Object, IFormatProvider ) methods.
Imports System
Imports System.Collections
Imports Microsoft.VisualBasic

Module IConvertibleProviderDemo

    ' Define the types of averaging available in the class 
    ' implementing IConvertible.
    Enum AverageType as Short
        None = 0
        GeometricMean = 1
        ArithmeticMean = 2
        Median = 3
    End Enum

    ' Pass an instance of this class to methods that require an 
    ' IFormatProvider. The class instance determines the type of 
    ' average to calculate.
    Public Class AverageInfo
        Implements IFormatProvider

        Protected  AvgType      As AverageType

        ' Specify the type of averaging in the constructor.
        Public Sub New(
 avgType As AverageType )
            Me.AvgType = avgType
        End Sub

        ' This method returns a reference to the containing object 
        ' if an object of AverageInfo type is requested. 
        Public Function GetFormat( argType
 As Type ) As Object _
            Implements IFormatProvider.GetFormat

            If argType Is GetType(
 AverageInfo ) Then
                Return Me
            Else
                Return Nothing
            End If
        End Function 

        ' Use this property to set or get the type of averaging.
        Public Property TypeOfAverage( ) As
 AverageType
            Get
                Return Me.AvgType
            End Get
            Set( ByVal value as
 AverageType )
                Me.AvgType = value
            End Set
        End Property
    End Class 

    ' This class encapsulates an array of Double values and implements
 
    ' the IConvertible interface. Most of the IConvertible methods 
    ' return an average of the array elements in one of three types:
 
    ' arithmetic mean, geometric mean, or median. 
    Public Class DataSet
        Implements IConvertible

        Protected data              As ArrayList
        Protected defaultProvider   As AverageInfo
           
        ' Construct the object and add an initial list of values.
        ' Create a default format provider.
        Public Sub New(
 ParamArray values( ) As Double
 )
            data = New ArrayList( values )
            defaultProvider = New AverageInfo( _
                AverageType.ArithmeticMean )  
        End Sub
           
        ' Add additional values with this method.
        Public Function Add( value As
 Double ) As Integer
            data.Add( value )
            Return data.Count
        End Function
           
        ' Get, set, and add values with this indexer property.
        Default Public Property
 Item(index As Integer) As
 Double
            Get
                If index >= 0 AndAlso index
 < data.Count Then
                    Return System.Convert.ToDouble( data( index
 ) )
                Else
                    Throw New InvalidOperationException(
 _
                        "[DataSet.get] Index out of range."
 )
                End If
            End Get
            Set
                If index >= 0 AndAlso index
 < data.Count Then
                    data( index ) = value
                 
                ElseIf index = data.Count Then
                    data.Add( value )
                Else
                    Throw New InvalidOperationException(
 _
                        "[DataSet.set] Index out of range."
 )
                End If
            End Set
        End Property
          
        ' This property returns the number of elements in the object.
        Public ReadOnly Property
 Count( ) As Integer
            Get
                Return data.Count
            End Get
        End Property

        ' This method calculates the average of the object's elements.
        Protected Function Average( ByVal
 avgType As AverageType ) As Double

            Dim SumProd As Double
 
            Dim Index   As Integer

            If data.Count = 0 Then Return
 0.0

            Select Case avgType
                
                Case AverageType.GeometricMean

                    SumProd = 1.0
                    For Index = 0 To data.Count
 - 1
                        SumProd *= data( Index )
                    Next Index
                    
                    ' This calculation will not fail with negative 
                    ' elements.
                    Return Math.Sign( SumProd ) * Math.Pow( _
                        Math.Abs( SumProd ), 1.0 / data.Count )

                Case AverageType.ArithmeticMean

                    SumProd = 0.0
                    For Index = 0 To data.Count
 - 1
                        SumProd += data( Index )
                    Next Index

                    Return SumProd / data.Count 

                Case AverageType.Median

                    If data.Count Mod 2 = 0
 Then
                        Return ( data( data.Count \ 2 ) + _
                            data( data.Count \ 2 - 1 ) ) / 2.0
                    Else
                        Return data( data.Count \ 2 ) 
                    End If
            End Select
        End Function

        ' Get the AverageInfo object from the caller's format 
        ' provider, or use the local default.
        Protected Function GetAverageInfo(
 _
            provider As IFormatProvider ) As
 AverageInfo

            Dim avgInfo As AverageInfo = Nothing

            If Not provider Is
 Nothing Then
                avgInfo = provider.GetFormat( GetType( AverageInfo
 ) )
            End If

            Return IIf( avgInfo Is Nothing,
 defaultProvider, avgInfo )
            
        End Function           

        ' Calculate the average and limit the range.
        Protected Function CalcNLimitAverage(
 min As Double, _
            max As Double, provider as
 IFormatProvider ) As Double

            ' Get the format provider and calculate the average.
            Dim avgInfo As AverageInfo = GetAverageInfo(
 provider )
            Dim avg As Double
 = Average( avgInfo.TypeOfAverage )

            ' Limit the range, based on the minimum and maximum values
 
            ' for the type.
            Return IIf( avg > max, max, IIf( avg < min,
 min, avg ) )

        End Function

        ' The following elements are required by IConvertible.

        ' None of these conversion functions throw exceptions. When
        ' the data is out of range for the type, the appropriate
        ' MinValue or MaxValue is used.
        Public Function GetTypeCode( ) As
 TypeCode _
            Implements IConvertible.GetTypeCode
            Return TypeCode.Object
        End Function

        Function ToBoolean( ByVal provider
 As IFormatProvider ) As _
            Boolean Implements IConvertible.ToBoolean

            ' ToBoolean is false if the dataset is empty.
            If data.Count <= 0 Then
                Return False

            ' For median averaging, ToBoolean is true if any 
            ' non-discarded elements are nonzero.
            ElseIf AverageType.Median = _
                GetAverageInfo( provider ).TypeOfAverage Then

                If data.Count Mod 2 = 0 Then
                    Return ( data( data.Count \ 2 ) <> 0.0
 Or _
                        data( data.Count \ 2 - 1 ) <> 0.0 )
                Else
                    Return data( data.Count \ 2 ) <> 0.0
                End If

            ' For arithmetic or geometric mean averaging, ToBoolean
 is 
            ' true if any element of the dataset is nonzero.  
            Else
                Dim Index As Integer
                For Index = 0 To data.Count
 - 1
                    If data( Index ) <> 0.0 Then
 Return True
                Next Index
                Return False
            End If
        End Function

        Function ToByte( ByVal provider As
 IFormatProvider ) As Byte _
            Implements IConvertible.ToByte
            Return Convert.ToByte( CalcNLimitAverage( _
                Byte.MinValue, Byte.MaxValue,
 provider ) )
        End Function

        Function ToChar( ByVal provider As
 IFormatProvider ) As Char _
            Implements IConvertible.ToChar
            Return Convert.ToChar( Convert.ToUInt16( _
                CalcNLimitAverage( 0.0, &HFFFF, provider ) ) )
        End Function

        ' Convert to DateTime by adding the calculated average as 
        ' seconds to the current date and time. A valid DateTime is
 
        ' always returned.
        Function ToDateTime( ByVal provider
 As IFormatProvider ) As _
            DateTime Implements IConvertible.ToDateTime
            Dim seconds As Double
 = Average( _
                GetAverageInfo( provider ).TypeOfAverage )
            Try
                Return DateTime.Now.AddSeconds( seconds )
            Catch ex As ArgumentOutOfRangeException
 
                Return IIf( seconds < 0.0, DateTime.MinValue,
 _
                    DateTime.MaxValue )
            End Try
        End Function

        Function ToDecimal( ByVal provider
 As IFormatProvider ) As _
            Decimal Implements IConvertible.ToDecimal

            ' The Double conversion rounds Decimal.MinValue and
            ' Decimal.MaxValue to invalid Decimal values, so the 
            ' following limits must be used.
            Return Convert.ToDecimal( CalcNLimitAverage( _
                -79228162514264330000000000000.0, _
                79228162514264330000000000000.0, provider ) )
        End Function

        Function ToDouble( ByVal provider As
 IFormatProvider) As _
            Double Implements IConvertible.ToDouble
            Return Average( GetAverageInfo( provider ).TypeOfAverage
 )
        End Function

        Function ToInt16( ByVal provider As
 IFormatProvider ) As _
            Short Implements IConvertible.ToInt16
            Return Convert.ToInt16( CalcNLimitAverage( _
                Int16.MinValue, Int16.MaxValue, provider ) )
        End Function

        Function ToInt32( ByVal provider As
 IFormatProvider ) As _
            Integer Implements IConvertible.ToInt32
            Return Convert.ToInt32( CalcNLimitAverage( _
                Int32.MinValue, Int32.MaxValue, provider ) )
        End Function

        Function ToInt64( ByVal provider As
 IFormatProvider ) As Long _
            Implements IConvertible.ToInt64

            ' The Double conversion rounds Int64.MinValue and 
            ' Int64.MaxValue to invalid Long values, so the following
 
            ' limits must be used.
            Return Convert.ToInt64( CalcNLimitAverage( _
                -9223372036854775000, 9223372036854775000, provider ) )
        End Function

        Function ToSByte( ByVal provider As
 IFormatProvider ) As _
            SByte Implements IConvertible.ToSByte

            ' SByte.MinValue and SByte.MaxValue are not defined in
            ' Visual Basic.
            Return Convert.ToSByte( CalcNLimitAverage( _
                -128, 127, provider ) )
        End Function

        Function ToSingle( ByVal provider As
 IFormatProvider ) As _
            Single Implements IConvertible.ToSingle
            Return Convert.ToSingle( CalcNLimitAverage( _
                Single.MinValue, Single.MaxValue,
 provider ) )
        End Function

        Function ToUInt16( ByVal provider As
 IFormatProvider ) As _
            UInt16 Implements IConvertible.ToUInt16

            ' UInt16.MinValue and UInt16.MaxValue are not defined in
 
            ' Visual Basic.
            Return Convert.ToUInt16( CalcNLimitAverage( _
                0, &HFFFF, provider ) )
        End Function

        Function ToUInt32( ByVal provider As
 IFormatProvider ) As _
            UInt32 Implements IConvertible.ToUInt32

            ' UInt32.MinValue and UInt32.MaxValue are not defined in
 
            ' Visual Basic.
            Return Convert.ToUInt32( CalcNLimitAverage( _
                0, 4294967295, provider ) )
        End Function

        Function ToUInt64( ByVal provider As
 IFormatProvider ) As _
            UInt64 Implements IConvertible.ToUInt64

            ' UInt64.MinValue and UInt64.MaxValue are not defined in
 
            ' Visual Basic. The Double conversion would have rounded
 
            ' UInt64.MaxValue, so the following limit must be used.
            Return Convert.ToUInt64( CalcNLimitAverage( _
                0, 18446744073709550000.0, provider ) )
        End Function

        Function ToType( ByVal conversionType
 As Type, _
            ByVal provider As IFormatProvider)
 As Object _
            Implements IConvertible.ToType
            Return Convert.ChangeType( Average( GetAverageInfo(
 _
                provider ).TypeOfAverage ), conversionType )
        End Function

        Overloads Function ToString( ByVal
 provider As IFormatProvider _
            ) As String Implements
 IConvertible.ToString
            Dim avgType as AverageType = _
                GetAverageInfo( provider ).TypeOfAverage
            Return String.Format( "(
 {0}: {1:G10} )", avgType, _
                Average( avgType ) )
        End Function
    End Class
   
    ' Display a DataSet with three different format providers.
    Sub DisplayDataSet( ds As DataSet )

        Dim fmt    As String
      = "{0,-12}{1,20}{2,20}{3,20}"
        Dim median As AverageInfo = New
 AverageInfo( AverageType.Median )
        Dim geMean As AverageInfo = _
            New AverageInfo( AverageType.GeometricMean )
        Dim iX     As Integer

        ' Display the dataset elements.
        If ds.Count > 0 Then
            Console.Write( vbCrLf & "DataSet: [{0}",
 ds( 0 ) )
            For iX = 1 To ds.Count - 1
                Console.Write( ", {0}", ds( iX ) )
            Next iX
            Console.WriteLine( "]" & vbCrLf )
        End If

        Console.WriteLine( fmt, "Convert.", "Default",
 _
            "Geometric Mean", "Median"
 )
        Console.WriteLine( fmt, "--------", "-------",
 _
            "--------------", "------"
 )
        Console.WriteLine( fmt, "ToBoolean", _
            Convert.ToBoolean( ds, Nothing ), _
            Convert.ToBoolean( ds, geMean ), _
            Convert.ToBoolean( ds, median ) )
        Console.WriteLine( fmt, "ToByte", _
            Convert.ToByte( ds, Nothing ), _
            Convert.ToByte( ds, geMean ), _
            Convert.ToByte( ds, median ) )
        Console.WriteLine( fmt, "ToChar", _
            Convert.ToChar( ds, Nothing ), _
            Convert.ToChar( ds, geMean ), _
            Convert.ToChar( ds, median ) )
        Console.WriteLine( "{0,-12}{1,20:yyyy-MM-dd HH:mm:ss}"
 & _
            "{2,20:yyyy-MM-dd HH:mm:ss}{3,20:yyyy-MM-dd HH:mm:ss}",
 _
            "ToDateTime", Convert.ToDateTime( ds,
 Nothing ), _
            Convert.ToDateTime( ds, geMean ), _
            Convert.ToDateTime( ds, median ) )
        Console.WriteLine( fmt, "ToDecimal", _
            Convert.ToDecimal( ds, Nothing ), _
            Convert.ToDecimal( ds, geMean ), _
            Convert.ToDecimal( ds, median ) )
        Console.WriteLine( fmt, "ToDouble", _
            Convert.ToDouble( ds, Nothing ), _
            Convert.ToDouble( ds, geMean ), _
            Convert.ToDouble( ds, median ) )
        Console.WriteLine( fmt, "ToInt16", _
            Convert.ToInt16( ds, Nothing ), _
            Convert.ToInt16( ds, geMean ), _
            Convert.ToInt16( ds, median ) )
        Console.WriteLine( fmt, "ToInt32", _
            Convert.ToInt32( ds, Nothing ), _
            Convert.ToInt32( ds, geMean ), _
            Convert.ToInt32( ds, median ) )
        Console.WriteLine( fmt, "ToInt64", _
            Convert.ToInt64( ds, Nothing ), _
            Convert.ToInt64( ds, geMean ), _
            Convert.ToInt64( ds, median ) )
        Console.WriteLine( fmt, "ToSByte", _
            Convert.ToSByte( ds, Nothing ), _
            Convert.ToSByte( ds, geMean ), _
            Convert.ToSByte( ds, median ) )
        Console.WriteLine( fmt, "ToSingle", _
            Convert.ToSingle( ds, Nothing ), _
            Convert.ToSingle( ds, geMean ), _
            Convert.ToSingle( ds, median ) )
        Console.WriteLine( fmt, "ToUInt16", _
            Convert.ToUInt16( ds, Nothing ), _
            Convert.ToUInt16( ds, geMean ), _
            Convert.ToUInt16( ds, median ) )
        Console.WriteLine( fmt, "ToUInt32", _
            Convert.ToUInt32( ds, Nothing ), _
            Convert.ToUInt32( ds, geMean ), _
            Convert.ToUInt32( ds, median ) )
        Console.WriteLine( fmt, "ToUInt64", _
            Convert.ToUInt64( ds, Nothing ), _
            Convert.ToUInt64( ds, geMean ), _
            Convert.ToUInt64( ds, median ) )
    End Sub
   
    Sub Main( )
        Console.WriteLine( _
            "This example of the Convert.ToXXX( Object, "
 & _
            "IFormatProvider ) methods " & vbCrLf
 & "generates " & _
            "the following output. The example displays the "
 & _
            "values " & vbCrLf & "returned
 by the methods, " & _
            "using several IFormatProvider objects."
 & vbCrLf )
          
        Dim ds1 As New DataSet(
 10.5, 22.2, 45.9, 88.7, 156.05, 297.6 )
        DisplayDataSet( ds1 )
          
        Dim ds2 As New DataSet(
 _
            359999.95, 425000, 499999.5, 775000, 1695000 )
        DisplayDataSet( ds2 )
    End Sub 
End Module 

' This example of the Convert.ToXXX( Object, IFormatProvider ) methods
' generates the following output. The example displays the values
' returned by the methods, using several IFormatProvider objects.
' 
' DataSet: [10.5, 22.2, 45.9, 88.7, 156.05, 297.6]
' 
' Convert.                 Default      Geometric Mean             
 Median
' --------                 -------      --------------             
 ------
' ToBoolean                   True                True             
   True
' ToByte                       103                  59             
     67
' ToChar                         g                   ;             
      C
' ToDateTime   2003-05-13 14:52:53 2003-05-13 14:52:09 2003-05-13 14:52:17
' ToDecimal       103.491666666667    59.4332135445164             
   67.3
' ToDouble        103.491666666667    59.4332135445164             
   67.3
' ToInt16                      103                  59             
     67
' ToInt32                      103                  59             
     67
' ToInt64                      103                  59             
     67
' ToSByte                      103                  59             
     67
' ToSingle                103.4917            59.43321             
   67.3
' ToUInt16                     103                  59             
     67
' ToUInt32                     103                  59             
     67
' ToUInt64                     103                  59             
     67
' 
' DataSet: [359999.95, 425000, 499999.5, 775000, 1695000]
' 
' Convert.                 Default      Geometric Mean             
 Median
' --------                 -------      --------------             
 ------
' ToBoolean                   True                True             
   True
' ToByte                       255                 255             
    255
' ToChar                         ?                   ?             
      ?
' ToDateTime   2003-05-22 07:27:49 2003-05-20 22:17:27 2003-05-19 09:44:29
' ToDecimal              750999.89    631577.237188435            499999.5
' ToDouble               750999.89    631577.237188435            499999.5
' ToInt16                    32767               32767             
  32767
' ToInt32                   751000              631577             
 500000
' ToInt64                   751000              631577             
 500000
' ToSByte                      127                 127             
    127
' ToSingle                750999.9            631577.3            499999.5
' ToUInt16                   65535               65535             
  65535
' ToUInt32                  751000              631577             
 500000
' ToUInt64                  751000              631577             
 500000

// Example of the Convert.ToXXX( object, IFormatProvider ) methods.
using System;
using System.Collections;

// Define the types of averaging available in the class 
// implementing IConvertible.
public enum AverageType : short
{
    None = 0,
    GeometricMean = 1,
    ArithmeticMean = 2,
    Median = 3
};

// Pass an instance of this class to methods that require an 
// IFormatProvider. The class instance determines the type of 
// average to calculate.
public class AverageInfo : IFormatProvider
{
    protected AverageType AvgType;

    // Specify the type of averaging in the constructor.
    public AverageInfo( AverageType avgType )
    {
        this.AvgType = avgType;
    }

    // This method returns a reference to the containing object 
    // if an object of AverageInfo type is requested. 
    public object GetFormat( Type argType )
    {
        if ( argType == typeof( AverageInfo ) )
            return this;
        else
            return null;
    }

    // Use this property to set or get the type of averaging.
    public AverageType TypeOfAverage        
    {
        get { return this.AvgType;
 }
        set { this.AvgType = value; }
    }
}

// This class encapsulates an array of double values and implements
 
// the IConvertible interface. Most of the IConvertible methods 
// return an average of the array elements in one of three types: 
// arithmetic mean, geometric mean, or median. 
public class DataSet : IConvertible
{
    protected ArrayList     data;
    protected AverageInfo   defaultProvider;
        
    // Construct the object and add an initial list of values.
    // Create a default format provider.
    public DataSet( params double[ ] values )
    {
        data = new ArrayList( values );
        defaultProvider = 
            new AverageInfo( AverageType.ArithmeticMean );
    }
        
    // Add additional values with this method.
    public int Add( double value )
    {
        data.Add( value );
        return data.Count;
    }
        
    // Get, set, and add values with this indexer property.
    public double this[ int
 index ]        
    {
        get
        {
            if( index >= 0 && index < data.Count
 )
                return (double)data[ index ];
            else
                throw new InvalidOperationException(
                    "[DataSet.get] Index out of range."
 );
        }
        set
        {
            if( index >= 0 && index < data.Count
 )
                data[ index ] = value;

            else if( index == data.Count )
                data.Add( value );
            else
                throw new InvalidOperationException(
                    "[DataSet.set] Index out of range."
 );
        }
    }
        
    // This property returns the number of elements in the object.
    public int Count        
    {
        get { return data.Count; }
    }

    // This method calculates the average of the object's elements.
    protected double Average( AverageType avgType )
    {
        double  SumProd;

        if( data.Count == 0 ) 
            return 0.0;

        switch( avgType )
        {
            case AverageType.GeometricMean:

                SumProd = 1.0;
                for( int Index = 0; Index <
 data.Count; Index++ )
                    SumProd *= (double)data[ Index ];
                
                // This calculation will not fail with negative 
                // elements.
                return Math.Sign( SumProd ) * Math.Pow( 
                    Math.Abs( SumProd ), 1.0 / data.Count );

            case AverageType.ArithmeticMean:

                SumProd = 0.0;
                for( int Index = 0; Index <
 data.Count; Index++ )
                    SumProd += (double)data[ Index ];

                return SumProd / data.Count;

            case AverageType.Median:

                if( data.Count % 2 == 0 )
                    return ( (double)data[ data.Count / 2 ] +
 
                        (double)data[ data.Count / 2 - 1 ] ) / 2.0;
                else
                    return (double)data[ data.Count / 2 ];

            default:
                return 0.0;
        }
    }

    // Get the AverageInfo object from the caller's format provider
,
    // or use the local default.
    protected AverageInfo GetAverageInfo( IFormatProvider provider
 )
    {
        AverageInfo avgInfo = null;

        if( provider != null )
            avgInfo = (AverageInfo)provider.GetFormat( 
                typeof( AverageInfo ) );

        if ( avgInfo == null )
            return defaultProvider;
        else
            return avgInfo;
    }

    // Calculate the average and limit the range.
    protected double CalcNLimitAverage( double min, double max,
 
        IFormatProvider provider )
    {
        // Get the format provider and calculate the average.
        AverageInfo avgInfo = GetAverageInfo( provider );
        double avg = Average( avgInfo.TypeOfAverage );

        // Limit the range, based on the minimum and maximum values
 
        // for the type.
        return avg > max ? max : avg < min ? min : avg;

    }

    // The following elements are required by IConvertible.

    // None of these conversion functions throw exceptions. When
    // the data is out of range for the type, the appropriate
    // MinValue or MaxValue is used.
    public TypeCode GetTypeCode( )
    {
        return TypeCode.Object;
    }

    public bool ToBoolean( IFormatProvider
 provider )
    {
        // ToBoolean is false if the dataset is empty.
        if( data.Count <= 0 )
            return false;

        // For median averaging, ToBoolean is true if any 
        // non-discarded elements are nonzero.
        else if( AverageType.Median == 
            GetAverageInfo( provider ).TypeOfAverage )
        {
            if (data.Count % 2 == 0 )
                return ( (double)data[ data.Count / 2 ] != 0.0
 || 
                    (double)data[ data.Count / 2 - 1 ] != 0.0 );
            else
                return (double)data[ data.Count / 2 ] != 0.0;
        }

        // For arithmetic or geometric mean averaging, ToBoolean is
 
        // true if any element of the dataset is nonzero.  
        else
        {
            for( int Index = 0; Index <
 data.Count; Index++ )
                if( (double)data[ Index ] != 0.0 ) 
                    return true;
            return false;
        }
    }

    public byte ToByte( IFormatProvider provider )
    {
        return Convert.ToByte( CalcNLimitAverage( 
            Byte.MinValue, Byte.MaxValue, provider ) );
    }

    public char ToChar( IFormatProvider provider
 )
    {
        return Convert.ToChar( Convert.ToUInt16( CalcNLimitAverage(
 
            Char.MinValue, Char.MaxValue, provider ) ) );
    }

    // Convert to DateTime by adding the calculated average as 
    // seconds to the current date and time. A valid DateTime is 
    // always returned.
    public DateTime ToDateTime( IFormatProvider provider )
    {
        double seconds = 
            Average( GetAverageInfo( provider ).TypeOfAverage );
        try
        {
            return DateTime.Now.AddSeconds( seconds );
        }
        catch( ArgumentOutOfRangeException )
        {
            return seconds < 0.0 ? DateTime.MinValue : DateTime.MaxValue;
        }
    }

    public decimal ToDecimal( IFormatProvider provider )
    {
        // The Double conversion rounds Decimal.MinValue and 
        // Decimal.MaxValue to invalid Decimal values, so the 
        // following limits must be used.
        return Convert.ToDecimal( CalcNLimitAverage( 
            -79228162514264330000000000000.0, 
            79228162514264330000000000000.0, provider ) );
    }

    public double ToDouble( IFormatProvider provider )
    {
        return Average( GetAverageInfo(provider).TypeOfAverage
 );
    }

    public short ToInt16( IFormatProvider provider )
    {
        return Convert.ToInt16( CalcNLimitAverage( 
            Int16.MinValue, Int16.MaxValue, provider ) );
    }

    public int ToInt32( IFormatProvider provider
 )
    {
        return Convert.ToInt32( CalcNLimitAverage( 
            Int32.MinValue, Int32.MaxValue, provider ) );
    }

    public long ToInt64( IFormatProvider provider )
    {
        // The Double conversion rounds Int64.MinValue and 
        // Int64.MaxValue to invalid Int64 values, so the following
 
        // limits must be used.
        return Convert.ToInt64( CalcNLimitAverage( 
            -9223372036854775000, 9223372036854775000, provider ) );
    }

    public SByte ToSByte( IFormatProvider provider )
    {
        return Convert.ToSByte( CalcNLimitAverage( 
            SByte.MinValue, SByte.MaxValue, provider ) );
    }

    public float ToSingle( IFormatProvider
 provider )
    {
        return Convert.ToSingle( CalcNLimitAverage( 
            Single.MinValue, Single.MaxValue, provider ) );
    }

    public UInt16 ToUInt16( IFormatProvider provider )
    {
        return Convert.ToUInt16( CalcNLimitAverage( 
            UInt16.MinValue, UInt16.MaxValue, provider ) );
    }

    public UInt32 ToUInt32( IFormatProvider provider )
    {
        return Convert.ToUInt32( CalcNLimitAverage( 
            UInt32.MinValue, UInt32.MaxValue, provider ) );
    }

    public UInt64 ToUInt64( IFormatProvider provider )
    {
        // The Double conversion rounds UInt64.MaxValue to an invalid
        // UInt64 value, so the following limit must be used.
        return Convert.ToUInt64( CalcNLimitAverage( 
            0, 18446744073709550000.0, provider ) );
    }

    public object ToType( Type conversionType, 
        IFormatProvider provider )
    {
        return Convert.ChangeType( Average( 
            GetAverageInfo( provider ).TypeOfAverage ), 
            conversionType );
    }

    public string ToString( IFormatProvider
 provider )
    {
        AverageType avgType = GetAverageInfo( provider ).TypeOfAverage;
        return String.Format( "( {0}: {1:G10} )", avgType,
 
            Average( avgType ) );
    }
}
   
class IConvertibleProviderDemo
{
    // Display a DataSet with three different format providers.
    public static void DisplayDataSet(
 DataSet ds )
    {
        string      fmt    = "{0,-12}{1,20}{2,20}{3,20}";
        AverageInfo median = new AverageInfo( AverageType.Median
 );
        AverageInfo geMean = 
            new AverageInfo( AverageType.GeometricMean );

         // Display the dataset elements.
        if( ds.Count > 0 )
        {
            Console.Write( "\nDataSet: [{0}", ds[ 0 ] );
            for( int iX = 1; iX < ds.Count;
 iX++ )
                Console.Write( ", {0}", ds[ iX ] );
            Console.WriteLine( "]\n" );
        }

        Console.WriteLine( fmt, "Convert.", "Default", 
            "Geometric Mean", "Median");
        Console.WriteLine( fmt, "--------", "-------", 
            "--------------", "------");
        Console.WriteLine( fmt, "ToBoolean", 
            Convert.ToBoolean( ds, null ), 
            Convert.ToBoolean( ds, geMean ), 
            Convert.ToBoolean( ds, median ) );
        Console.WriteLine( fmt, "ToByte", 
            Convert.ToByte( ds, null ), 
            Convert.ToByte( ds, geMean ), 
            Convert.ToByte( ds, median ) );
        Console.WriteLine( fmt, "ToChar", 
            Convert.ToChar( ds, null ), 
            Convert.ToChar( ds, geMean ), 
            Convert.ToChar( ds, median ) );
        Console.WriteLine( "{0,-12}{1,20:yyyy-MM-dd HH:mm:ss}" +
            "{2,20:yyyy-MM-dd HH:mm:ss}{3,20:yyyy-MM-dd HH:mm:ss}", 
            "ToDateTime", Convert.ToDateTime( ds, null
 ), 
            Convert.ToDateTime( ds, geMean ), 
            Convert.ToDateTime( ds, median ) );
        Console.WriteLine( fmt, "ToDecimal", 
            Convert.ToDecimal( ds, null ), 
            Convert.ToDecimal( ds, geMean ), 
            Convert.ToDecimal( ds, median ) );
        Console.WriteLine( fmt, "ToDouble", 
            Convert.ToDouble( ds, null ), 
            Convert.ToDouble( ds, geMean ), 
            Convert.ToDouble( ds, median ) );
        Console.WriteLine( fmt, "ToInt16", 
            Convert.ToInt16( ds, null ), 
            Convert.ToInt16( ds, geMean ), 
            Convert.ToInt16( ds, median ) );
        Console.WriteLine( fmt, "ToInt32", 
            Convert.ToInt32( ds, null ), 
            Convert.ToInt32( ds, geMean ), 
            Convert.ToInt32( ds, median ) );
        Console.WriteLine( fmt, "ToInt64", 
            Convert.ToInt64( ds, null ), 
            Convert.ToInt64( ds, geMean ), 
            Convert.ToInt64( ds, median ) );
        Console.WriteLine( fmt, "ToSByte", 
            Convert.ToSByte( ds, null ), 
            Convert.ToSByte( ds, geMean ), 
            Convert.ToSByte( ds, median ) );
        Console.WriteLine( fmt, "ToSingle", 
            Convert.ToSingle( ds, null ), 
            Convert.ToSingle( ds, geMean ), 
            Convert.ToSingle( ds, median ) );
        Console.WriteLine( fmt, "ToUInt16", 
            Convert.ToUInt16( ds, null ), 
            Convert.ToUInt16( ds, geMean ), 
            Convert.ToUInt16( ds, median ) );
        Console.WriteLine( fmt, "ToUInt32", 
            Convert.ToUInt32( ds, null ), 
            Convert.ToUInt32( ds, geMean ), 
            Convert.ToUInt32( ds, median ) );
        Console.WriteLine( fmt, "ToUInt64", 
            Convert.ToUInt64( ds, null ), 
            Convert.ToUInt64( ds, geMean ), 
            Convert.ToUInt64( ds, median ) );
    }
   
    public static void Main(
 )
    {
        Console.WriteLine( "This example of " +
            "the Convert.ToXXX( object, IFormatProvider ) methods " +
            "\ngenerates the following output. The example " +
            "displays the values \nreturned by the methods, " +
            "using several IFormatProvider objects.\n"
 );
          
        DataSet ds1 = new DataSet( 
            10.5, 22.2, 45.9, 88.7, 156.05, 297.6 );
        DisplayDataSet( ds1 );
          
        DataSet ds2 = new DataSet( 
            359999.95, 425000, 499999.5, 775000, 1695000 );
        DisplayDataSet( ds2 );
    }
}

/*
This example of the Convert.ToXXX( object, IFormatProvider ) methods
generates the following output. The example displays the values
returned by the methods, using several IFormatProvider objects.

DataSet: [10.5, 22.2, 45.9, 88.7, 156.05, 297.6]

Convert.                 Default      Geometric Mean              Median
--------                 -------      --------------              ------
ToBoolean                   True                True                True
ToByte                       103                  59                  67
ToChar                         g                   ;                   C
ToDateTime   2003-05-13 15:04:12 2003-05-13 15:03:28 2003-05-13 15:03:35
ToDecimal       103.491666666667    59.4332135445164                67.3
ToDouble        103.491666666667    59.4332135445164                67.3
ToInt16                      103                  59                  67
ToInt32                      103                  59                  67
ToInt64                      103                  59                  67
ToSByte                      103                  59                  67
ToSingle                103.4917            59.43321                67.3
ToUInt16                     103                  59                  67
ToUInt32                     103                  59                  67
ToUInt64                     103                  59                  67

DataSet: [359999.95, 425000, 499999.5, 775000, 1695000]

Convert.                 Default      Geometric Mean              Median
--------                 -------      --------------              ------
ToBoolean                   True                True                True
ToByte                       255                 255                 255
ToChar                         ?                   ?                   ?
ToDateTime   2003-05-22 07:39:08 2003-05-20 22:28:45 2003-05-19 09:55:48
ToDecimal              750999.89    631577.237188435            499999.5
ToDouble               750999.89    631577.237188435            499999.5
ToInt16                    32767               32767               32767
ToInt32                   751000              631577              500000
ToInt64                   751000              631577              500000
ToSByte                      127                 127                 127
ToSingle                750999.9            631577.3            499999.5
ToUInt16                   65535               65535               65535
ToUInt32                  751000              631577              500000
ToUInt64                  751000              631577              500000
*/

C++

// Example of the Convert::ToXXX( Object*, IFormatProvider* ) methods.
using namespace System;
using namespace System::Collections;

// Define the types of averaging available in the class 
// implementing IConvertible.
enum class AverageType : short
{
   None = 0,
   GeometricMean = 1,
   ArithmeticMean = 2,
   Median = 3
};


// Pass an instance of this class to methods that require an 
// IFormatProvider. The class instance determines the type of 
// average to calculate.
ref class AverageInfo: public IFormatProvider
{
protected:
   AverageType AvgType;

public:

   // Specify the type of averaging in the constructor.
   AverageInfo( AverageType avgType )
   {
      this->AvgType = avgType;
   }


   // This method returns a reference to the containing object 
   // if an object of AverageInfo type is requested. 
   virtual Object^ GetFormat( Type^ argType )
   {
      if ( argType == AverageInfo::typeid)
            return this;
      else
            return (Object^)0;
   }


   property AverageType TypeOfAverage 
   {

      // Use this property to set or get the type of averaging.
      AverageType get()
      {
         return this->AvgType;
      }

      void set( AverageType value )
      {
         this->AvgType = value;
      }

   }

};


// This class encapsulates an array of double values and implements
 
// the IConvertible interface. Most of the IConvertible methods 
// return an average of the array elements in one of three types: 
// arithmetic mean, geometric mean, or median. 
ref class DataSet: public IConvertible
{
private:
   static Object^ null = nullptr;

protected:
   ArrayList^ data;
   AverageInfo^ defaultProvider;

   // This method unboxes a boxed double.
   double UnBoxDouble( Object^ obj )
   {
      return  *static_cast<double^>(obj);
   }


public:

   // Construct the object and add an initial list of values.
   // Create a default format provider.
   DataSet( ... array<Double>^values )
   {
      data = gcnew ArrayList( (Array^)values );
      defaultProvider = gcnew AverageInfo( AverageType::ArithmeticMean );
   }


   // Add additional values with this method.
   int Add( double value )
   {
      data->Add( value );
      return data->Count;
   }


   property double Item[ int ]
   {

      // Get, set, and add values with this indexer property.
      double get( int index )
      {
         if ( index >= 0 && index < data->Count
 )
                  return UnBoxDouble( data[ index ] );
         else
                  throw gcnew InvalidOperationException( "[DataSet.get]
 Index out of range." );
      }

      void set( int index,
 double value )
      {
         if ( index >= 0 && index < data->Count
 )
                  data[ index ] = value;
         else
         if ( index == data->Count )
                  data->Add( value );
         else
                  throw gcnew InvalidOperationException( "[DataSet.set]
 Index out of range." );
      }

   }

   property int Count 
   {

      // This property returns the number of elements in the object.
      int get()
      {
         return data->Count;
      }

   }

protected:

   // This method calculates the average of the object's elements.
   double Average( AverageType avgType )
   {
      double SumProd;
      if ( data->Count == 0 )
            return 0.0;

      switch ( avgType )
      {
         case AverageType::GeometricMean:
            SumProd = 1.0;
            for ( int Index = 0; Index <
 data->Count; Index++ )
               SumProd *= UnBoxDouble( data[ Index ] );
            
            // This calculation will not fail with negative 
            // elements.
            return Math::Sign( SumProd ) * Math::Pow( Math::Abs(
 SumProd ), 1.0 / data->Count );

         case AverageType::ArithmeticMean:
            SumProd = 0.0;
            for ( int Index = 0; Index <
 data->Count; Index++ )
               SumProd += UnBoxDouble( data[ Index ] );
            return SumProd / data->Count;

         case AverageType::Median:
            if ( data->Count % 2 == 0 )
                        return (UnBoxDouble( data[ data->Count
 / 2 ] ) + UnBoxDouble( data[ data->Count / 2 - 1 ] )) / 2.0;
            else
                        return UnBoxDouble( data[ data->Count
 / 2 ] );

         default:
            return 0.0;
      }
   }


   // Get the AverageInfo object from the caller's format provider,
   // or use the local default.
   AverageInfo^ GetAverageInfo( IFormatProvider^ provider )
   {
      AverageInfo^ avgInfo = nullptr;
      if ( provider != nullptr )
            avgInfo = static_cast<AverageInfo^>(provider->GetFormat( AverageInfo::typeid
 ));

      if ( avgInfo == nullptr )
            return defaultProvider;
      else
            return avgInfo;
   }


   // Calculate the average and limit the range.
   double CalcNLimitAverage( double min, double max, IFormatProvider^ provider )
   {
      
      // Get the format provider and calculate the average.
      AverageInfo^ avgInfo = GetAverageInfo( provider );
      double avg = Average( avgInfo->TypeOfAverage );
      
      // Limit the range, based on the minimum and maximum values 
      // for the type.
      return avg > max ? max : avg < min ? min : avg;
   }


public:

   // The following elements are required by IConvertible.
   // None of these conversion functions throw exceptions. When
   // the data is out of range for the type, the appropriate
   // MinValue or MaxValue is used.
   virtual TypeCode GetTypeCode()
   {
      return TypeCode::Object;
   }

   virtual bool ToBoolean( IFormatProvider^ provider )
   {
      
      // ToBoolean is false if the dataset is empty.
      if ( data->Count <= 0 )
            return false;
      // For median averaging, ToBoolean is true if any 
      // non-discarded elements are nonzero.
      else
      
      // For median averaging, ToBoolean is true if any 
      // non-discarded elements are nonzero.
      if ( AverageType::Median == GetAverageInfo( provider )->TypeOfAverage
 )
      {
         if ( data->Count % 2 == 0 )
                  return (UnBoxDouble( data[ data->Count /
 2 ] ) != 0.0 || UnBoxDouble( data[ data->Count / 2 - 1 ] ) != 0.0);
         else
                  return UnBoxDouble( data[ data->Count / 2
 ] ) != 0.0;
      }
      // For arithmetic or geometric mean averaging, ToBoolean is 
      // true if any element of the dataset is nonzero.  
      else
      {
         for ( int Index = 0; Index < data->Count;
 Index++ )
            if ( UnBoxDouble( data[ Index ] ) != 0.0 )
                        return true;
         return false;
      }
   }

   virtual Byte ToByte( IFormatProvider^ provider )
   {
      return Convert::ToByte( CalcNLimitAverage( Byte::MinValue,
 Byte::MaxValue, provider ) );
   }

   virtual Char ToChar( IFormatProvider^ provider )
   {
      return Convert::ToChar( Convert::ToUInt16( CalcNLimitAverage(
 Char::MinValue, Char::MaxValue, provider ) ) );
   }


   // Convert to DateTime by adding the calculated average as 
   // seconds to the current date and time. A valid DateTime is 
   // always returned.
   virtual DateTime ToDateTime( IFormatProvider^ provider )
   {
      double seconds = Average( GetAverageInfo( provider )->TypeOfAverage );
      try
      {
         return DateTime::Now.AddSeconds( seconds );
      }
      catch ( ArgumentOutOfRangeException^ ) 
      {
         return seconds < 0.0 ? DateTime::MinValue : DateTime::MaxValue;
      }

   }

   virtual Decimal ToDecimal( IFormatProvider^ provider )
   {
      
      // The Double conversion rounds Decimal.MinValue and 
      // Decimal.MaxValue to invalid Decimal values, so the 
      // following limits must be used.
      return Convert::ToDecimal( CalcNLimitAverage(  -79228162514264330000000000000.0,
 79228162514264330000000000000.0, provider ) );
   }

   virtual double ToDouble( IFormatProvider^ provider )
   {
      return Average( GetAverageInfo( provider )->TypeOfAverage
 );
   }

   virtual short ToInt16( IFormatProvider^ provider )
   {
      return Convert::ToInt16( CalcNLimitAverage( Int16::MinValue,
 Int16::MaxValue, provider ) );
   }

   virtual int ToInt32( IFormatProvider^ provider )
   {
      return Convert::ToInt32( CalcNLimitAverage( Int32::MinValue,
 Int32::MaxValue, provider ) );
   }

   virtual __int64 ToInt64( IFormatProvider^ provider )
   {
      
      // The Double conversion rounds Int64.MinValue and 
      // Int64.MaxValue to invalid Int64 values, so the following 
      // limits must be used.
      return Convert::ToInt64( CalcNLimitAverage(  -9223372036854775000,
 9223372036854775000, provider ) );
   }

   virtual signed char ToSByte( IFormatProvider^ provider )
   {
      return Convert::ToSByte( CalcNLimitAverage( SByte::MinValue,
 SByte::MaxValue, provider ) );
   }

   virtual float ToSingle( IFormatProvider^ provider )
   {
      return Convert::ToSingle( CalcNLimitAverage( Single::MinValue,
 Single::MaxValue, provider ) );
   }

   virtual UInt16 ToUInt16( IFormatProvider^ provider )
   {
      return Convert::ToUInt16( CalcNLimitAverage( UInt16::MinValue,
 UInt16::MaxValue, provider ) );
   }

   virtual UInt32 ToUInt32( IFormatProvider^ provider )
   {
      return Convert::ToUInt32( CalcNLimitAverage( UInt32::MinValue,
 UInt32::MaxValue, provider ) );
   }

   virtual UInt64 ToUInt64( IFormatProvider^ provider )
   {
      
      // The Double conversion rounds UInt64.MaxValue to an invalid
      // UInt64 value, so the following limit must be used.
      return Convert::ToUInt64( CalcNLimitAverage( 0, 18446744073709550000.0,
 provider ) );
   }

   virtual Object^ ToType( Type^ conversionType, IFormatProvider^ provider )
   {
      return Convert::ChangeType( Average( GetAverageInfo( provider
 )->TypeOfAverage ), conversionType );
   }

   virtual String^ ToString( IFormatProvider^ provider )
   {
      AverageType avgType = GetAverageInfo( provider )->TypeOfAverage;
      return String::Format( "( {0}: {1:G10} )", avgType,
 Average( avgType ) );
   }

};


// Display a DataSet with three different format providers.
void DisplayDataSet( DataSet^ ds )
{
   IFormatProvider^ null = nullptr;
   String^ fmt = "{0,-12}{1,20}{2,20}{3,20}";
   AverageInfo^ median = gcnew AverageInfo( AverageType::Median );
   AverageInfo^ geMean = gcnew AverageInfo( AverageType::GeometricMean );
   
   // Display the dataset elements.
   if ( ds->Count > 0 )
   {
      Console::Write( "\nDataSet: [{0}", ds->Item[ 0 ] );
      for ( int iX = 1; iX < ds->Count;
 iX++ )
         Console::Write( ", {0}", ds->Item[ iX ] );
      Console::WriteLine( "]\n" );
   }

   Console::WriteLine( fmt, "Convert::", "Default", "Geometric
 Mean", "Median" );
   Console::WriteLine( fmt, "---------", "-------", "--------------",
 "------" );
   Console::WriteLine( fmt, "ToBoolean", Convert::ToBoolean( ds, null
 ), Convert::ToBoolean( ds, geMean ), Convert::ToBoolean( ds, median ) );
   Console::WriteLine( fmt, "ToByte", Convert::ToByte( ds, null
 ), Convert::ToByte( ds, geMean ), Convert::ToByte( ds, median ) );
   Console::WriteLine( fmt, "ToChar", Convert::ToChar( ds, null
 ), Convert::ToChar( ds, geMean ), Convert::ToChar( ds, median ) );
   Console::WriteLine( "{0,-12}{1,20:yyyy-MM-dd HH:mm:ss}"
   "{2,20:yyyy-MM-dd HH:mm:ss}{3,20:yyyy-MM-dd HH:mm:ss}", "ToDateTime",
 Convert::ToDateTime( ds, null ), Convert::ToDateTime( ds, geMean
 ), Convert::ToDateTime( ds, median ) );
   Console::WriteLine( fmt, "ToDecimal", Convert::ToDecimal( ds, null
 ), Convert::ToDecimal( ds, geMean ), Convert::ToDecimal( ds, median ) );
   Console::WriteLine( fmt, "ToDouble", Convert::ToDouble( ds, null
 ), Convert::ToDouble( ds, geMean ), Convert::ToDouble( ds, median ) );
   Console::WriteLine( fmt, "ToInt16", Convert::ToInt16( ds, null
 ), Convert::ToInt16( ds, geMean ), Convert::ToInt16( ds, median ) );
   Console::WriteLine( fmt, "ToInt32", Convert::ToInt32( ds, null
 ), Convert::ToInt32( ds, geMean ), Convert::ToInt32( ds, median ) );
   Console::WriteLine( fmt, "ToInt64", Convert::ToInt64( ds, null
 ), Convert::ToInt64( ds, geMean ), Convert::ToInt64( ds, median ) );
   Console::WriteLine( fmt, "ToSByte", Convert::ToSByte( ds, null
 ), Convert::ToSByte( ds, geMean ), Convert::ToSByte( ds, median ) );
   Console::WriteLine( fmt, "ToSingle", Convert::ToSingle( ds, null
 ), Convert::ToSingle( ds, geMean ), Convert::ToSingle( ds, median ) );
   Console::WriteLine( fmt, "ToUInt16", Convert::ToUInt16( ds, null
 ), Convert::ToUInt16( ds, geMean ), Convert::ToUInt16( ds, median ) );
   Console::WriteLine( fmt, "ToUInt32", Convert::ToUInt32( ds, null
 ), Convert::ToUInt32( ds, geMean ), Convert::ToUInt32( ds, median ) );
   Console::WriteLine( fmt, "ToUInt64", Convert::ToUInt64( ds, null
 ), Convert::ToUInt64( ds, geMean ), Convert::ToUInt64( ds, median ) );
}

int main()
{
   Console::WriteLine( "This example of the "
   "Convert::ToXXX( Object*, IFormatProvider* ) methods "
   "\ngenerates the following output. The example "
   "displays the values \nreturned by the methods, "
   "using several IFormatProvider objects.\n" );
   
   // To call a [ParamArray] method in C++, you cannot just
   // list the parameters, you need to build an array.
   array<Double>^dataElem = gcnew array<Double>(6);
   dataElem[ 0 ] = 10.5;
   dataElem[ 1 ] = 22.2;
   dataElem[ 2 ] = 45.9;
   dataElem[ 3 ] = 88.7;
   dataElem[ 4 ] = 156.05;
   dataElem[ 5 ] = 297.6;
   DataSet^ ds1 = gcnew DataSet( dataElem );
   DisplayDataSet( ds1 );
   dataElem = gcnew array<Double>(5);
   dataElem[ 0 ] = 359999.95;
   dataElem[ 1 ] = 425000;
   dataElem[ 2 ] = 499999.5;
   dataElem[ 3 ] = 775000;
   dataElem[ 4 ] = 1695000;
   DataSet^ ds2 = gcnew DataSet( dataElem );
   DisplayDataSet( ds2 );
}

/*
This example of the Convert::ToXXX( Object*, IFormatProvider* ) methods
generates the following output. The example displays the values
returned by the methods, using several IFormatProvider objects.

DataSet: [10.5, 22.2, 45.9, 88.7, 156.05, 297.6]

Convert::                Default      Geometric Mean              Median
---------                -------      --------------              ------
ToBoolean                   True                True                True
ToByte                       103                  59                  67
ToChar                         g                   ;                   C
ToDateTime   2003-05-13 15:30:23 2003-05-13 15:29:39 2003-05-13 15:29:47
ToDecimal       103.491666666667    59.4332135445164                67.3
ToDouble        103.491666666667    59.4332135445164                67.3
ToInt16                      103                  59                  67
ToInt32                      103                  59                  67
ToInt64                      103                  59                  67
ToSByte                      103                  59                  67
ToSingle                103.4917            59.43321                67.3
ToUInt16                     103                  59                  67
ToUInt32                     103                  59                  67
ToUInt64                     103                  59                  67

DataSet: [359999.95, 425000, 499999.5, 775000, 1695000]

Convert::                Default      Geometric Mean              Median
---------                -------      --------------              ------
ToBoolean                   True                True                True
ToByte                       255                 255                 255
ToChar                         ?                   ?                   ?
ToDateTime   2003-05-22 08:05:19 2003-05-20 22:54:57 2003-05-19 10:21:59
ToDecimal              750999.89    631577.237188435            499999.5
ToDouble               750999.89    631577.237188435            499999.5
ToInt16                    32767               32767               32767
ToInt32                   751000              631577              500000
ToInt64                   751000              631577              500000
ToSByte                      127                 127                 127
ToSingle                750999.9            631577.3            499999.5
ToUInt16                   65535               65535               65535
ToUInt32                  751000              631577              500000
ToUInt64                  751000              631577              500000
*/

// Example of the Convert.ToXXX( object, IFormatProvider ) methods.
import System.* ;
import System.Collections.* ;

// Define the types of averaging available in the class 
// implementing IConvertible.
public class AverageType
{
    public static final short None = 0;
    public static final short GeometricMean
 = 1;
    public static final short ArithmeticMean
 = 2;
    public static final short Median = 3;
} //AverageType
// Pass an instance of this class to methods that require an 
// IFormatProvider. The class instance determines the type of 
// average to calculate.
public class AverageInfo implements IFormatProvider
{
    protected int avgType;   

    // Specify the type of averaging in the constructor.
    public AverageInfo(int  avgType) 
    {
        this.avgType = avgType;
    } //AverageInfo

    // This method returns a reference to the containing object 
    // if an object of AverageInfo type is requested. 
    public Object GetFormat(Type argType) 
    {
        if ( argType == AverageInfo.class.ToType())
 {
            return this ;
        }
        else {
            return null ;
        }
    } //GetFormat 

    // Use this property to set or get the type of averaging.
    /** @property 
     */
    public int get_TypeOfAverage()
    {
        return this.avgType ;
    } //get_TypeOfAverage

    /** @property 
     */
    public void set_TypeOfAverage(int
 value )
    {
        this.avgType = value;
    } //set_TypeOfAverage
} //AverageInfo


// This class encapsulates an array of double values and implements
 
// the IConvertible interface. Most of the IConvertible methods 
// return an average of the array elements in one of three types: 
// arithmetic mean, geometric mean, or median. 
public class DataSet implements IConvertible
{
    protected ArrayList data;
    protected AverageInfo defaultProvider;

    // Construct the object and add an initial list of values.
    // Create a default format provider.
    public DataSet(double values[])
    {
        data = new ArrayList(values);
        defaultProvider = new AverageInfo(AverageType.ArithmeticMean);
    } //DataSet

    // Add additional values with this method.
    public int Add(double value) 
    {
        data.Add(new Double(value));
        return data.get_Count() ;
    } //Add

    // Get, set, and add values with this indexer property.
    /** @property 
     */
    public double get_Item(int index) throws
 InvalidOperationException
    {
        if ((index >= 0) && (index < data.get_Count()))
 {
            return Convert.ToDouble((data.get_Item(index))) ;
        }
        else {
            throw new InvalidOperationException(
                "[DataSet.get] Index out of range.")
 ;
        }
    } //get_Item

    /** @property 
     */
    public void set_Item(int
 index, double value) 
        throws InvalidOperationException
    {
        if ((index >= 0) && (index < data.get_Count()))
 {
            data.set_Item( index ,(Int64) value );
        }
        else {
            if ( index == data.get_Count()  ) {
                data.Add((Int64)value);
            }
            else {            
                throw new InvalidOperationException(
                    "[DataSet.set] Index out of range.")
 ;
            }
        }
    } //set_Item

    // This property returns the number of elements in the object.
    /** @property 
     */
    public int get_Count()
    {
        return data.get_Count() ;
    } //get_Count

    // This method calculates the average of the object's elements.
    protected double Average(int avgType)
    {
        double SumProd;

        if ( data.get_Count() == 0  ) {
            return 0.0 ;
        }

        if (avgType == AverageType.GeometricMean) { 
            SumProd = 1.0;
            for(int index =0 ; index < data.get_Count();
 index++) {        
                SumProd = SumProd * Convert.ToDouble((data.get_Item(index)));
            }  
            // This calculation will not fail with negative 
            // elements.
            return System.Math.Sign(SumProd) 
                * System.Math.Pow(System.Math.Abs(SumProd), 
                1.0 / data.get_Count());
        }
        else if (avgType == AverageType.ArithmeticMean
 ) { 
            SumProd = 0.0;
            for(int Index=0; Index < data.get_Count();
 Index++) {
                SumProd += Convert.ToDouble((data.get_Item(Index)));
            }  
            return SumProd / data.get_Count() ;
        }
        else if (avgType == AverageType.Median
 ) {
            if ( (data.get_Count() % 2) == 0 ) {
                return ((Convert.ToDouble(data.get_Item(data.get_Count()
 / 2))
                    + Convert.ToDouble(data.get_Item(data.get_Count() 
                    / 2 - 1))) / 2.0);
            }
            else {        
                return Convert.ToDouble(((data.get_Item((data.get_Count()
 
                    / 2))))) ;
            }
        }
        else {
            return 0.0 ;
        }
    } //Average


    // Get the AverageInfo object from the caller's format provider
,
    // or use the local default.
    protected AverageInfo GetAverageInfo(IFormatProvider provider)
    {
        AverageInfo avgInfo = null;

        if ( provider  != null  ) {
            avgInfo =((AverageInfo)(provider.GetFormat(
                    AverageInfo.class.ToType())));
        }

        if ( avgInfo == null  ) {
            return defaultProvider ;
        }
        else {        
            return avgInfo ;
        }
    } //GetAverageInfo

    // Calculate the average and limit the range.
    protected double CalcNLimitAverage(
        double min, double max, IFormatProvider provider)
    {
        // Get the format provider and calculate the average.
        AverageInfo avgInfo = GetAverageInfo(provider);
        double avg = Average(avgInfo.get_TypeOfAverage());

        // Limit the range, based on the minimum and maximum values
 
        // for the type.
        return(avg > max) ? max :(avg < min) ? min : avg
 ;
    } //CalcNLimitAverage

    // The following elements are required by IConvertible.
    // None of these conversion functions throw exceptions. When
    // the data is out of range for the type, the appropriate
    // MinValue or MaxValue is used.
    public TypeCode GetTypeCode()
    {
        return TypeCode.Object ;
    } //GetTypeCode

    public boolean ToBoolean(IFormatProvider provider) 
    {
        // ToBoolean is false if the dataset is empty.
        if ( data.get_Count() <= 0  ) {
            return false ;
        }

        // For median averaging, ToBoolean is true if any 
        // non-discarded elements are nonzero.
        else {
            if ( AverageType.Median == GetAverageInfo(
                provider).get_TypeOfAverage()  ) {
                if ( (data.get_Count() % 2) == 0  ) {
                    return Convert.ToDouble(data.get_Item((data.get_Count()
 
                        / 2))) != 0.0 || Convert.ToDouble(data.get_Item(
                        (data.get_Count() / 2 - 1))) != 0.0;
                }
                else {
                    return Convert.ToDouble(data.get_Item((data.get_Count()
 
                        / 2))) != 0.0;
                }
            }

            // For arithmetic or geometric mean averaging, ToBoolean is
 
            // true if any element of the dataset is nonzero.  
            else {
                for(int index=0; index <
 data.get_Count(); index++) {
                    if (Convert.ToDouble(data.get_Item(index))
 != 0.0) {
                        return true ;
                    }
                } 
                return false ;
            }
        }
    } //ToBoolean

    public ubyte ToByte(IFormatProvider provider)
    {
        return Convert.ToByte(CalcNLimitAverage(0, 255, provider));
    } //ToByte

    public char ToChar(IFormatProvider provider)
 
    {
        return Convert.ToChar(Convert.ToUInt16(CalcNLimitAverage(Char.MinValue
,
            Char.MaxValue, provider))) ;
    } //ToChar

    // Convert to DateTime by adding the calculated average as 
    // seconds to the current date and time. A valid DateTime is 
    // always returned.
    public DateTime ToDateTime(IFormatProvider provider)
    {
        double seconds = Average(GetAverageInfo(provider).get_TypeOfAverage());
        try {
            return DateTime.get_Now().AddSeconds(seconds) ;
        }
        catch(ArgumentOutOfRangeException exp) {
            return(seconds < 0.0) ? DateTime.MinValue : DateTime.MaxValue
 ;
        }
    } //ToDateTime

    public System.Decimal ToDecimal(IFormatProvider provider)
    {
        // The Double conversion rounds Decimal.MinValue and 
        // Decimal.MaxValue to invalid Decimal values, so the 
        // following limits must be used.
        return Convert.ToDecimal(CalcNLimitAverage(-7.92281625142643E+28,
 
            7.92281625142643E+28, provider)) ;
    } //ToDecimal

    public double ToDouble(IFormatProvider provider)
    {
        return Average(GetAverageInfo(provider).get_TypeOfAverage())
 ;
    } //ToDouble

    public short ToInt16(IFormatProvider provider)
    {
        return Convert.ToInt16(CalcNLimitAverage(Int16.MinValue,
 
            Int16.MaxValue, provider)) ;
    } //ToInt16

    public int ToInt32(IFormatProvider provider)
    {
        return Convert.ToInt32(CalcNLimitAverage(Int32.MinValue,
 Int32.MaxValue,
            provider)) ;
    } //ToInt32

    public long ToInt64(IFormatProvider provider) 
    {
        // The Double conversion rounds Int64.MinValue and 
        // Int64.MaxValue to invalid Int64 values, so the following
 
        // limits must be used.
        return Convert.ToInt64(CalcNLimitAverage(-9223372036854775000L,
 
            9223372036854775000L, provider)) ;
    } //ToInt64

    public byte ToSByte(IFormatProvider provider)
    {
        return Convert.ToSByte(CalcNLimitAverage(SByte.MinValue,
 SByte.MaxValue,
            provider)) ;
    } //ToSByte

    public float ToSingle(IFormatProvider provider)
    {
        return Convert.ToSingle(CalcNLimitAverage(Single.MinValue,
 
            Single.MaxValue, provider)) ;
    } //ToSingle

    public UInt16 ToUInt16(IFormatProvider provider)
    {
        return Convert.ToUInt16(CalcNLimitAverage(
            Convert.ToDouble(UInt16.MinValue), 
            Convert.ToDouble(UInt16.MaxValue), provider));
    } //ToUInt16

    public UInt32 ToUInt32(IFormatProvider provider)
    {
        return Convert.ToUInt32(CalcNLimitAverage(
            Convert.ToDouble(UInt32.MinValue), 
            Convert.ToDouble(UInt32.MaxValue), provider)) ;
    } //ToUInt32

    public UInt64 ToUInt64(IFormatProvider provider)
    {
        // The Double conversion rounds UInt64.MaxValue to an invalid
        // UInt64 value, so the following limit must be used.
        return Convert.ToUInt64(CalcNLimitAverage(0, 1.84467440737095E+19,
 
            provider)) ;
    } //ToUInt64

    public Object ToType(Type conversionType, IFormatProvider
 provider)
    {
        return Convert.ChangeType((System.Double)Average(
            GetAverageInfo(provider).get_TypeOfAverage()), conversionType) ;
    } //ToType


    public String ToString(IFormatProvider provider)
    {
        int avgType = GetAverageInfo(provider).get_TypeOfAverage();
        return String.Format("( {0}: {1} )", (Int32)avgType,
 
            ((System.Double)Average(avgType)).ToString("G10"));
    } //ToString
} //DataSet

class IConvertibleProviderDemo
{
    // Display a DataSet with three different format providers.
    public static void DisplayDataSet(DataSet
 ds) 
        throws InvalidOperationException
    {
        String fmt = "{0,-12}{1,20}{2,20}{3,20}";
        AverageInfo median =  new AverageInfo(AverageType.Median);
        AverageInfo geMean = new AverageInfo(AverageType.GeometricMean);

        // Display the dataset elements.
        if ( ds.get_Count() > 0  ) {
            Console.Write("\nDataSet: [{0}", (System.Double)ds.get_Item(
 0));
            for(int iX=1; iX < ds.get_Count();
 iX++) {            
                Console.Write(", {0}",(System.Double) ds.get_Item( iX));
            } 
            Console.WriteLine("]\n");
        }

        Console.WriteLine(fmt, new Object[] { "Convert.",
 "Default", 
            "Geometric Mean", "Median" });
        Console.WriteLine(fmt, new Object[] { "--------",
 "-------", 
            "--------------", "------" });
        Console.WriteLine(fmt, new Object[] { "ToBoolean",
 
            (System.Boolean)Convert.ToBoolean(ds, null),
            (System.Boolean)Convert.ToBoolean(ds, geMean),
            (System.Boolean)Convert.ToBoolean(ds, median) });
        Console.WriteLine(fmt, new Object[] { "ToByte",
 
            (Convert.ToString(Convert.ToByte(ds, null))), 
            (Convert.ToString(Convert.ToByte(ds, geMean))), 
            (Convert.ToString(Convert.ToByte(ds, median))) });
        Console.WriteLine(fmt, new Object[] { "ToChar",
 
            (Char)Convert.ToChar(ds, null), 
            (Char)Convert.ToChar(ds, geMean), 
            (Char)Convert.ToChar(ds, median) });
        Console.WriteLine("{0,-12}{1,20:yyyy-MM-dd HH:mm:ss}"
            + "{2,20:yyyy-MM-dd HH:mm:ss}{3,20:yyyy-MM-dd HH:mm:ss}",
            new Object[] { "ToDateTime", Convert.ToDateTime(ds,
 null), 
            Convert.ToDateTime(ds, geMean),    Convert.ToDateTime(ds, median) });
        Console.WriteLine(fmt, new Object[] { "ToDecimal",
 
            Convert.ToDecimal(ds, null), Convert.ToDecimal(ds,
 geMean), 
            Convert.ToDecimal(ds, median) });
        Console.WriteLine(fmt, new Object[] { "ToDouble",
 
            (System.Double)Convert.ToDouble(ds, null), 
            (System.Double)Convert.ToDouble(ds, geMean), 
            (System.Double)Convert.ToDouble(ds, median) });
        Console.WriteLine(fmt, new Object[] { "ToInt16",
 
            (System.Int16)Convert.ToInt16(ds, null), 
            (System.Int16)Convert.ToInt16(ds, geMean), 
            (System.Int16)Convert.ToInt16(ds, median) });
        Console.WriteLine(fmt, new Object[] { "ToInt32",
 
            (System.Int32)Convert.ToInt32(ds, null), 
            (System.Int32)Convert.ToInt32(ds, geMean), 
            (System.Int32)Convert.ToInt32(ds, median) });
        Console.WriteLine(fmt, new Object[] { "ToInt64",
 
            (System.Int64)Convert.ToInt64(ds, null), 
            (System.Int64)Convert.ToInt64(ds, geMean), 
            (System.Int64)Convert.ToInt64(ds, median) });
        Console.WriteLine(fmt, new Object[] { "ToSByte",
 
            (System.SByte)Convert.ToSByte(ds, null), 
            (System.SByte)Convert.ToSByte(ds, geMean), 
            (System.SByte)Convert.ToSByte(ds, median) });
        Console.WriteLine(fmt, new Object[] { "ToSingle",
 
            new Decimal(Convert.ToSingle(ds, null)),
 
            new Decimal(Convert.ToSingle(ds, geMean)), 
            new Decimal(Convert.ToSingle(ds, median) )});
        Console.WriteLine(fmt, new Object[] { "ToUInt16",
 
            Convert.ToUInt16(ds, null), 
            Convert.ToUInt16(ds, geMean), 
            Convert.ToUInt16(ds, median)});
        Console.WriteLine(fmt, new Object[] { "ToUInt32",
 
            Convert.ToUInt32(ds, null), 
            Convert.ToUInt32(ds, geMean), 
            Convert.ToUInt32(ds, median)});
        Console.WriteLine(fmt, new Object[] { "ToUInt64",
 
            Convert.ToUInt64(ds, null), 
            Convert.ToUInt64(ds, geMean), 
            Convert.ToUInt64(ds, median)});
    } //DisplayDataSet

    public static void main(String[]
 args) throws InvalidOperationException
    {
        Console.WriteLine(("This example of " 
            + "the Convert.ToXXX( object, IFormatProvider ) methods "
            + "\ngenerates the following output. The example " 
            + "displays the values \nreturned by the methods, " 
            + "using several IFormatProvider objects.\n"));

        DataSet ds1 = new DataSet(new double[]
 { 10.5, 22.2, 45.9, 88.7,
                    156.05, 297.6 });
        DisplayDataSet(ds1);
        DataSet ds2 = new DataSet(new double[]
 { 359999.95, 425000, 499999.5, 
                    775000, 1695000 });
        DisplayDataSet(ds2);
    } //main
} //IConvertibleProviderDemo

/*
This example of the Convert.ToXXX( object, IFormatProvider ) methods
generates the following output. The example displays the values
returned by the methods, using several IFormatProvider objects.

DataSet: [10.5, 22.2, 45.9, 88.7, 156.05, 297.6]

Convert.                 Default      Geometric Mean              Median
--------                 -------      --------------              ------
ToBoolean                   True                True                True
ToByte                       103                  59                  67
ToChar                         g                   ;                   C
ToDateTime   2003-05-13 15:04:12 2003-05-13 15:03:28 2003-05-13 15:03:35
ToDecimal       103.491666666667    59.4332135445164                67.3
ToDouble        103.491666666667    59.4332135445164                67.3
ToInt16                      103                  59                  67
ToInt32                      103                  59                  67
ToInt64                      103                  59                  67
ToSByte                      103                  59                  67
ToSingle                103.4917            59.43321                67.3
ToUInt16                     103                  59                  67
ToUInt32                     103                  59                  67
ToUInt64                     103                  59                  67

DataSet: [359999.95, 425000, 499999.5, 775000, 1695000]

Convert.                 Default      Geometric Mean              Median
--------                 -------      --------------              ------
ToBoolean                   True                True                True
ToByte                       255                 255                 255
ToChar                         ?                   ?                   ?
ToDateTime   2003-05-22 07:39:08 2003-05-20 22:28:45 2003-05-19 09:55:48
ToDecimal              750999.89    631577.237188435            499999.5
ToDouble               750999.89    631577.237188435            499999.5
ToInt16                    32767               32767               32767
ToInt32                   751000              631577              500000
ToInt64                   751000              631577              500000
ToSByte                      127                 127                 127
ToSingle                750999.9            631577.3            499999.5
ToUInt16                   65535               65535               65535
ToUInt32                  751000              631577              500000
ToUInt64                  751000              631577              500000
*/

プラットフォーム

バージョン情報

.NET Framework
サポート対象 : 2.0、1.1、1.0
.NET Compact Framework
サポート対象 : 2.0、1.0

参照

関連項目
Convert クラス
Convert メンバ
System 名前空間
Object

Convert.ToBoolean メソッド

指定した値を等価のブール値に変換します。
オーバーロードの一覧

名前	説明
Convert.ToBoolean (Boolean)	指定したブール値を返します。実際の変換処理は実行されません。 .NET Compact Framework によってサポートされています。
Convert.ToBoolean (Byte)	指定した 8 ビット符号なし整数の値を等価の Boolean 値に変換します。 .NET Compact Framework によってサポートされています。
Convert.ToBoolean (Char)	このメソッドを呼び出すと、必ず InvalidCastException がスローされます。 .NET Compact Framework によってサポートされています。
Convert.ToBoolean (DateTime)	このメソッドを呼び出すと、必ず InvalidCastException がスローされます。
Convert.ToBoolean (Decimal)	指定した Decimal の数値を等価のブール値に変換します。 .NET Compact Framework によってサポートされています。
Convert.ToBoolean (Double)	指定した倍精度浮動小数点数値を等価のブール値に変換します。 .NET Compact Framework によってサポートされています。
Convert.ToBoolean (Int16)	指定した 16 ビット符号付き整数の値を等価の Boolean 値に変換します。 .NET Compact Framework によってサポートされています。
Convert.ToBoolean (Int32)	指定した 32 ビット符号付き整数の値を等価の Boolean 値に変換します。 .NET Compact Framework によってサポートされています。
Convert.ToBoolean (Int64)	指定した 64 ビット符号付き整数の値を等価のブール値に変換します。 .NET Compact Framework によってサポートされています。
Convert.ToBoolean (Object)	指定した Object の値を等価のブール値に変換します。 .NET Compact Framework によってサポートされています。
Convert.ToBoolean (SByte)	指定した 8 ビット符号付き整数の値を等価のブール値に変換します。 .NET Compact Framework によってサポートされています。
Convert.ToBoolean (Single)	指定した単精度浮動小数点数を等価のブール値に変換します。 .NET Compact Framework によってサポートされています。
Convert.ToBoolean (String)	論理値の指定した String 形式を、それと等価なブール値に変換します。 .NET Compact Framework によってサポートされています。
Convert.ToBoolean (UInt16)	指定した 16 ビット符号なし整数の値を等価のブール値に変換します。 .NET Compact Framework によってサポートされています。
Convert.ToBoolean (UInt32)	指定した 32 ビット符号なし整数の値を等価のブール値に変換します。 .NET Compact Framework によってサポートされています。
Convert.ToBoolean (UInt64)	指定した 64 ビット符号なし整数の値を等価のブール値に変換します。 .NET Compact Framework によってサポートされています。
Convert.ToBoolean (Object, IFormatProvider)	指定したカルチャに固有の書式情報を使用して、指定した Object の値を等価のブール値に変換します。 .NET Compact Framework によってサポートされています。
Convert.ToBoolean (String, IFormatProvider)	指定したカルチャに固有の書式情報を使用して、指定した論理値の String 形式を等価のブール値に変換します。 .NET Compact Framework によってサポートされています。

参照

Convert.ToBoolean メソッド (Int64)

指定した 64 ビット符号付き整数の値を等価のブール値に変換します。

名前空間: System
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

Public Shared Function ToBoolean
 ( _
    value As Long _
) As Boolean

Visual Basic (使用法)

Dim value As Long
Dim returnValue As Boolean

returnValue = Convert.ToBoolean(value)

public static bool ToBoolean
 (
    long value
)

C++

public:
static bool ToBoolean (
    long long value
)

public static boolean ToBoolean (
    long value
)

JScript

public static function ToBoolean
 (
    value : long
) : boolean

パラメータ

value: 64 ビット符号付き整数。

戻り値
value が 0 以外の場合は true。0 の場合は false。

プラットフォーム

バージョン情報

.NET Framework
サポート対象 : 2.0、1.1、1.0
.NET Compact Framework
サポート対象 : 2.0、1.0

参照

関連項目
Convert クラス
Convert メンバ
System 名前空間
Int64

Convert.ToBoolean メソッド (Object)

指定した Object の値を等価のブール値に変換します。

名前空間: System
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

Public Shared Function ToBoolean
 ( _
    value As Object _
) As Boolean

Visual Basic (使用法)

Dim value As Object
Dim returnValue As Boolean

returnValue = Convert.ToBoolean(value)

public static bool ToBoolean
 (
    Object value
)

C++

public:
static bool ToBoolean (
    Object^ value
)

public static boolean ToBoolean (
    Object value
)

JScript

public static function ToBoolean
 (
    value : Object
) : boolean

パラメータ

value: IConvertible インターフェイスを実装する Object か、または null 参照 (Visual Basic では Nothing)。

戻り値
value が null 参照 (Visual Basic では Nothing) に等しい場合は false。または true または false。これは、基になる型の value に対して IConvertible.ToBoolean メソッドを実行した結果を示します。

使用例

ToBoolean メソッドを使用して、文字列値をブール型に変換する方法を次のコード例に示します。

Visual Basic

Public Sub ConvertStringBoolean(ByVal
 stringVal As String)

    Dim boolVal As Boolean
 = False

    Try
        boolVal = System.Convert.ToBoolean(stringVal)
        If boolVal Then
            System.Console.WriteLine( _
                "String is equal to System.Boolean.TrueString.")
        Else
            System.Console.WriteLine( _
                "String is equal to System.Boolean.FalseString.")
        End If
    Catch exception As System.FormatException
        System.Console.WriteLine( _
            "The string must equal System.Boolean.TrueString "
 + _
            "or System.Boolean.FalseString.")
    End Try

    ' A conversion from bool to string will always succeed.
    stringVal = System.Convert.ToString(boolVal)
    System.Console.WriteLine("{0} as a String is {1}",
 _
                              boolVal, stringVal)
End Sub

public void ConvertStringBoolean(string
 stringVal) {
    
    bool boolVal = false;

    try {
        boolVal = System.Convert.ToBoolean(stringVal);
        if (boolVal) {
            System.Console.WriteLine(
                "String was equal to System.Boolean.TrueString.");
        }
        else {
            System.Console.WriteLine(
                "String was equal to System.Boolean.FalseString.");
        }
    }
    catch (System.FormatException){
        System.Console.WriteLine(
            "The string must equal System.Boolean.TrueString
 " +
            "or System.Boolean.FalseString.");
    }

    // A conversion from bool to string will always succeed.
    stringVal = System.Convert.ToString(boolVal);
    System.Console.WriteLine("{0} as a string is {1}"
,
        boolVal, stringVal);
}

C++

public:
   void ConvertStringBoolean( String^ stringVal )
   {
      bool boolVal = false;

      try
      {
         boolVal = System::Convert::ToBoolean( stringVal );
         if ( boolVal )
         {
            System::Console::WriteLine(
               "String was equal to System::Boolean::TrueString." );
         }
         else
         {
            System::Console::WriteLine(
               "String was equal to System::Boolean::FalseString." );
         }
      }
      catch ( System::FormatException^ ) 
      {
         System::Console::WriteLine( "The String must equal System::Boolean::TrueString
 " +
            "or System::Boolean::FalseString." );
      }
      
      // A conversion from bool to String will always succeed.
      stringVal = System::Convert::ToString( boolVal );
      System::Console::WriteLine( " {0} as a String is {1}",
         boolVal, stringVal );
   }

public void ConvertStringBoolean(String stringVal)
{
    boolean boolVal = false;

    try {        
        boolVal = System.Convert.ToBoolean(stringVal);
        if (boolVal) {            
            System.Console.WriteLine(
                "String was equal to System.Boolean.TrueString.");
        }
        else {            
            System.Console.WriteLine(
                "String was equal to System.Boolean.FalseString.");
        }
    }
    catch (System.FormatException exp) {        
        System.Console.WriteLine(
            ("The string must equal System.Boolean.TrueString
 "  
            + "or System.Boolean.FalseString."));
    }

    // A conversion from bool to string will always succeed.
    stringVal = System.Convert.ToString(boolVal);
    System.Console.WriteLine("{0} as a string is {1}"
, 
        System.Convert.ToString(boolVal), stringVal);
} //ConvertStringBoolean

プラットフォーム

バージョン情報

.NET Framework
サポート対象 : 2.0、1.1、1.0
.NET Compact Framework
サポート対象 : 2.0、1.0

参照

関連項目
Convert クラス
Convert メンバ
System 名前空間
Object

Convert.ToBoolean メソッド (Byte)

指定した 8 ビット符号なし整数の値を等価の Boolean 値に変換します。

名前空間: System
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

Public Shared Function ToBoolean
 ( _
    value As Byte _
) As Boolean

Visual Basic (使用法)

Dim value As Byte
Dim returnValue As Boolean

returnValue = Convert.ToBoolean(value)

public static bool ToBoolean
 (
    byte value
)

C++

public:
static bool ToBoolean (
    unsigned char value
)

public static boolean ToBoolean (
    byte value
)

JScript

public static function ToBoolean
 (
    value : byte
) : boolean

パラメータ

value: 8 ビット符号なし整数。

戻り値
value が 0 以外の場合は true。0 の場合は false。

プラットフォーム

バージョン情報

.NET Framework
サポート対象 : 2.0、1.1、1.0
.NET Compact Framework
サポート対象 : 2.0、1.0

参照

Convert.ToBoolean メソッド (String, IFormatProvider)

指定したカルチャに固有の書式情報を使用して、指定した論理値の String 形式を等価のブール値に変換します。

名前空間: System
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

Public Shared Function ToBoolean
 ( _
    value As String, _
    provider As IFormatProvider _
) As Boolean

Visual Basic (使用法)

Dim value As String
Dim provider As IFormatProvider
Dim returnValue As Boolean

returnValue = Convert.ToBoolean(value, provider)

public static bool ToBoolean
 (
    string value,
    IFormatProvider provider
)

C++

public:
static bool ToBoolean (
    String^ value, 
    IFormatProvider^ provider
)

public static boolean ToBoolean (
    String value, 
    IFormatProvider provider
)

JScript

public static function ToBoolean
 (
    value : String, 
    provider : IFormatProvider
) : boolean

パラメータ

value: TrueString または FalseString のいずれかの値を格納する文字列。

provider: (予約済み) カルチャに固有の書式情報を提供する IFormatProvider インターフェイス実装。

戻り値
value が TrueString に等しい場合は true。value が FalseString または null 参照 (Visual Basic では Nothing) に等しい場合は false。

例外

例外の種類	条件
FormatException	value が TrueString または FalseString のいずれとも等しくありません。

解説

provider は無視され、この操作には関与しません。

使用例

ToBoolean を使用して String パラメータを受け取る方法については、次のコード例を参照してください。

Visual Basic

Public Sub ConvertStringBoolean(ByVal
 stringVal As String)

    Dim boolVal As Boolean
 = False

    Try
        boolVal = System.Convert.ToBoolean(stringVal)
        If boolVal Then
            System.Console.WriteLine( _
                "String is equal to System.Boolean.TrueString.")
        Else
            System.Console.WriteLine( _
                "String is equal to System.Boolean.FalseString.")
        End If
    Catch exception As System.FormatException
        System.Console.WriteLine( _
            "The string must equal System.Boolean.TrueString "
 + _
            "or System.Boolean.FalseString.")
    End Try

    ' A conversion from bool to string will always succeed.
    stringVal = System.Convert.ToString(boolVal)
    System.Console.WriteLine("{0} as a String is {1}",
 _
                              boolVal, stringVal)
End Sub

public void ConvertStringBoolean(string
 stringVal) {
    
    bool boolVal = false;

    try {
        boolVal = System.Convert.ToBoolean(stringVal);
        if (boolVal) {
            System.Console.WriteLine(
                "String was equal to System.Boolean.TrueString.");
        }
        else {
            System.Console.WriteLine(
                "String was equal to System.Boolean.FalseString.");
        }
    }
    catch (System.FormatException){
        System.Console.WriteLine(
            "The string must equal System.Boolean.TrueString
 " +
            "or System.Boolean.FalseString.");
    }

    // A conversion from bool to string will always succeed.
    stringVal = System.Convert.ToString(boolVal);
    System.Console.WriteLine("{0} as a string is {1}"
,
        boolVal, stringVal);
}

C++

public:
   void ConvertStringBoolean( String^ stringVal )
   {
      bool boolVal = false;

      try
      {
         boolVal = System::Convert::ToBoolean( stringVal );
         if ( boolVal )
         {
            System::Console::WriteLine(
               "String was equal to System::Boolean::TrueString." );
         }
         else
         {
            System::Console::WriteLine(
               "String was equal to System::Boolean::FalseString." );
         }
      }
      catch ( System::FormatException^ ) 
      {
         System::Console::WriteLine( "The String must equal System::Boolean::TrueString
 " +
            "or System::Boolean::FalseString." );
      }
      
      // A conversion from bool to String will always succeed.
      stringVal = System::Convert::ToString( boolVal );
      System::Console::WriteLine( " {0} as a String is {1}",
         boolVal, stringVal );
   }

public void ConvertStringBoolean(String stringVal)
{
    boolean boolVal = false;

    try {        
        boolVal = System.Convert.ToBoolean(stringVal);
        if (boolVal) {            
            System.Console.WriteLine(
                "String was equal to System.Boolean.TrueString.");
        }
        else {            
            System.Console.WriteLine(
                "String was equal to System.Boolean.FalseString.");
        }
    }
    catch (System.FormatException exp) {        
        System.Console.WriteLine(
            ("The string must equal System.Boolean.TrueString
 "  
            + "or System.Boolean.FalseString."));
    }

    // A conversion from bool to string will always succeed.
    stringVal = System.Convert.ToString(boolVal);
    System.Console.WriteLine("{0} as a string is {1}"
, 
        System.Convert.ToString(boolVal), stringVal);
} //ConvertStringBoolean

プラットフォーム

バージョン情報

.NET Framework
サポート対象 : 2.0、1.1、1.0
.NET Compact Framework
サポート対象 : 2.0、1.0

参照

関連項目
Convert クラス
Convert メンバ
System 名前空間
String

Convert.ToBoolean メソッド (SByte)

指定した 8 ビット符号付き整数の値を等価のブール値に変換します。

このメソッドは、CLS に準拠していません。

名前空間: System
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

<CLSCompliantAttribute(False)> _
Public Shared Function ToBoolean
 ( _
    value As SByte _
) As Boolean

Visual Basic (使用法)

Dim value As SByte
Dim returnValue As Boolean

returnValue = Convert.ToBoolean(value)

[CLSCompliantAttribute(false)] 
public static bool ToBoolean
 (
    sbyte value
)

C++

[CLSCompliantAttribute(false)] 
public:
static bool ToBoolean (
    signed char value
)

/** @attribute CLSCompliantAttribute(false) */ 
public static boolean ToBoolean (
    SByte value
)

JScript

CLSCompliantAttribute(false) 
public static function ToBoolean
 (
    value : sbyte
) : boolean

パラメータ

value: 8 ビット符号付き整数。

戻り値
value が 0 以外の場合は true。0 の場合は false。

プラットフォーム

バージョン情報

.NET Framework
サポート対象 : 2.0、1.1、1.0
.NET Compact Framework
サポート対象 : 2.0、1.0

参照

関連項目
Convert クラス
Convert メンバ
System 名前空間
SByte

Convert.ToBoolean メソッド (Int16)

指定した 16 ビット符号付き整数の値を等価の Boolean 値に変換します。

名前空間: System
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

Public Shared Function ToBoolean
 ( _
    value As Short _
) As Boolean

Visual Basic (使用法)

Dim value As Short
Dim returnValue As Boolean

returnValue = Convert.ToBoolean(value)

public static bool ToBoolean
 (
    short value
)

C++

public:
static bool ToBoolean (
    short value
)

public static boolean ToBoolean (
    short value
)

JScript

public static function ToBoolean
 (
    value : short
) : boolean

パラメータ

value: 16 ビット符号付き整数。

戻り値
value が 0 以外の場合は true。0 の場合は false。

プラットフォーム

バージョン情報

.NET Framework
サポート対象 : 2.0、1.1、1.0
.NET Compact Framework
サポート対象 : 2.0、1.0

参照

関連項目
Convert クラス
Convert メンバ
System 名前空間
Int16

Convert.ToBoolean メソッド (Double)

指定した倍精度浮動小数点数値を等価のブール値に変換します。

名前空間: System
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

Public Shared Function ToBoolean
 ( _
    value As Double _
) As Boolean

Visual Basic (使用法)

Dim value As Double
Dim returnValue As Boolean

returnValue = Convert.ToBoolean(value)

public static bool ToBoolean
 (
    double value
)

C++

public:
static bool ToBoolean (
    double value
)

public static boolean ToBoolean (
    double value
)

JScript

public static function ToBoolean
 (
    value : double
) : boolean

パラメータ

value: 倍精度浮動小数点数。

戻り値
value が 0 以外の場合は true。0 の場合は false。

使用例

ToBoolean メソッドを使用して、パラメータとして Double を受け取る方法を次のコード例に示します。

Visual Basic

Public Sub ConvertDoubleBool(ByVal
 doubleVal As Double)
    Dim boolVal As Boolean

    'Double to Boolean conversion cannot overflow.
    boolVal = System.Convert.ToBoolean(doubleVal)
    System.Console.WriteLine("{0} as a Boolean is: {1}.",
 _
                              doubleVal, boolVal)

    'Boolean to Double conversion cannot overflow.
    doubleVal = System.Convert.ToDouble(boolVal)
    System.Console.WriteLine("{0} as a Double is: {1}.",
 _
                              boolVal, doubleVal)
End Sub

public void ConvertDoubleBool(double doubleVal)
 {
    bool    boolVal;
    // Double to bool conversion cannot overflow.
    boolVal = System.Convert.ToBoolean(doubleVal);
    System.Console.WriteLine("{0} as a Boolean is: {1}.",
        doubleVal, boolVal);

    // bool to double conversion cannot overflow.
    doubleVal = System.Convert.ToDouble(boolVal);
    System.Console.WriteLine("{0} as a double is: {1}.",
        boolVal, doubleVal);
}

C++

public:
   void ConvertDoubleBool( double doubleVal )
   {
      bool boolVal;
      
      // Double to bool conversion cannot overflow.
      boolVal = System::Convert::ToBoolean( doubleVal );
      System::Console::WriteLine( " {0} as a Boolean is: {1}.",
         doubleVal, boolVal );
      
      // bool to double conversion cannot overflow.
      doubleVal = System::Convert::ToDouble( boolVal );
      System::Console::WriteLine( " {0} as a double is: {1}.",
         boolVal, doubleVal );
   }

public void ConvertDoubleBool(double doubleVal)
{
    boolean boolVal;

    // Double to bool conversion cannot overflow.
    boolVal = System.Convert.ToBoolean(doubleVal);
    System.Console.WriteLine("{0} as a Boolean is: {1}.", 
        System.Convert.ToString(doubleVal), 
        System.Convert.ToString(boolVal));

    // bool to double conversion cannot overflow.
    doubleVal = System.Convert.ToDouble(boolVal);
    System.Console.WriteLine("{0} as a double is: {1}.", 
        System.Convert.ToString(boolVal), 
        System.Convert.ToString(doubleVal));
} //ConvertDoubleBool

プラットフォーム

バージョン情報

.NET Framework
サポート対象 : 2.0、1.1、1.0
.NET Compact Framework
サポート対象 : 2.0、1.0

参照

関連項目
Convert クラス
Convert メンバ
System 名前空間
Double

Convert.ToBoolean メソッド (UInt64)

指定した 64 ビット符号なし整数の値を等価のブール値に変換します。

このメソッドは、CLS に準拠していません。

名前空間: System
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

<CLSCompliantAttribute(False)> _
Public Shared Function ToBoolean
 ( _
    value As ULong _
) As Boolean

Visual Basic (使用法)

Dim value As ULong
Dim returnValue As Boolean

returnValue = Convert.ToBoolean(value)

[CLSCompliantAttribute(false)] 
public static bool ToBoolean
 (
    ulong value
)

C++

[CLSCompliantAttribute(false)] 
public:
static bool ToBoolean (
    usigned long long value
)

/** @attribute CLSCompliantAttribute(false) */ 
public static boolean ToBoolean (
    UInt64 value
)

JScript

CLSCompliantAttribute(false) 
public static function ToBoolean
 (
    value : ulong
) : boolean

パラメータ

value: 64 ビット符号なし整数。

戻り値
value が 0 以外の場合は true。0 の場合は false。

プラットフォーム

バージョン情報

.NET Framework
サポート対象 : 2.0、1.1、1.0
.NET Compact Framework
サポート対象 : 2.0、1.0

参照

関連項目
Convert クラス
Convert メンバ
System 名前空間
UInt64

Convert.ToBoolean メソッド (Single)

指定した単精度浮動小数点数を等価のブール値に変換します。

名前空間: System
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

Public Shared Function ToBoolean
 ( _
    value As Single _
) As Boolean

Visual Basic (使用法)

Dim value As Single
Dim returnValue As Boolean

returnValue = Convert.ToBoolean(value)

public static bool ToBoolean
 (
    float value
)

C++

public:
static bool ToBoolean (
    float value
)

public static boolean ToBoolean (
    float value
)

JScript

public static function ToBoolean
 (
    value : float
) : boolean

パラメータ

value: 単精度浮動小数点数。

戻り値
value が 0 以外の場合は true。0 の場合は false。

プラットフォーム

バージョン情報

.NET Framework
サポート対象 : 2.0、1.1、1.0
.NET Compact Framework
サポート対象 : 2.0、1.0

参照

関連項目
Convert クラス
Convert メンバ
System 名前空間
Single

Convert.ToBoolean メソッド (Decimal)

指定した Decimal の数値を等価のブール値に変換します。

名前空間: System
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

Public Shared Function ToBoolean
 ( _
    value As Decimal _
) As Boolean

Visual Basic (使用法)

Dim value As Decimal
Dim returnValue As Boolean

returnValue = Convert.ToBoolean(value)

public static bool ToBoolean
 (
    decimal value
)

C++

public:
static bool ToBoolean (
    Decimal value
)

public static boolean ToBoolean (
    Decimal value
)

JScript

public static function ToBoolean
 (
    value : decimal
) : boolean

パラメータ

value: Decimal の数値。

戻り値
value が 0 以外の場合は true。0 の場合は false。

プラットフォーム

バージョン情報

.NET Framework
サポート対象 : 2.0、1.1、1.0
.NET Compact Framework
サポート対象 : 2.0、1.0

参照

関連項目
Convert クラス
Convert メンバ
System 名前空間
Decimal

Convert.ToBoolean メソッド (Boolean)

指定したブール値を返します。実際の変換処理は実行されません。

名前空間: System
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

Public Shared Function ToBoolean
 ( _
    value As Boolean _
) As Boolean

Visual Basic (使用法)

Dim value As Boolean
Dim returnValue As Boolean

returnValue = Convert.ToBoolean(value)

public static bool ToBoolean
 (
    bool value
)

C++

public:
static bool ToBoolean (
    bool value
)

public static boolean ToBoolean (
    boolean value
)

JScript

public static function ToBoolean
 (
    value : boolean
) : boolean

パラメータ

value: ブール値。

戻り値
パラメータ value は変更されずに返されます。

プラットフォーム

バージョン情報

.NET Framework
サポート対象 : 2.0、1.1、1.0
.NET Compact Framework
サポート対象 : 2.0、1.0

参照

Convert.ToBoolean メソッド (String)

論理値の指定した String 形式を、それと等価なブール値に変換します。

名前空間: System
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

Public Shared Function ToBoolean
 ( _
    value As String _
) As Boolean

Visual Basic (使用法)

Dim value As String
Dim returnValue As Boolean

returnValue = Convert.ToBoolean(value)

public static bool ToBoolean
 (
    string value
)

C++

public:
static bool ToBoolean (
    String^ value
)

public static boolean ToBoolean (
    String value
)

JScript

public static function ToBoolean
 (
    value : String
) : boolean

パラメータ

value: TrueString または FalseString の値を格納した String。

戻り値
value が TrueString に等しい場合は true。value が FalseString または null 参照 (Visual Basic では Nothing) に等しい場合は false。

例外

例外の種類	条件
FormatException	value が TrueString または FalseString のいずれとも等しくありません。

使用例

ToBoolean を使用して String パラメータを受け取る方法については、次のコード例を参照してください。

Visual Basic

Public Sub ConvertStringBoolean(ByVal
 stringVal As String)

    Dim boolVal As Boolean
 = False

    Try
        boolVal = System.Convert.ToBoolean(stringVal)
        If boolVal Then
            System.Console.WriteLine( _
                "String is equal to System.Boolean.TrueString.")
        Else
            System.Console.WriteLine( _
                "String is equal to System.Boolean.FalseString.")
        End If
    Catch exception As System.FormatException
        System.Console.WriteLine( _
            "The string must equal System.Boolean.TrueString "
 + _
            "or System.Boolean.FalseString.")
    End Try

    ' A conversion from bool to string will always succeed.
    stringVal = System.Convert.ToString(boolVal)
    System.Console.WriteLine("{0} as a String is {1}",
 _
                              boolVal, stringVal)
End Sub

public void ConvertStringBoolean(string
 stringVal) {
    
    bool boolVal = false;

    try {
        boolVal = System.Convert.ToBoolean(stringVal);
        if (boolVal) {
            System.Console.WriteLine(
                "String was equal to System.Boolean.TrueString.");
        }
        else {
            System.Console.WriteLine(
                "String was equal to System.Boolean.FalseString.");
        }
    }
    catch (System.FormatException){
        System.Console.WriteLine(
            "The string must equal System.Boolean.TrueString
 " +
            "or System.Boolean.FalseString.");
    }

    // A conversion from bool to string will always succeed.
    stringVal = System.Convert.ToString(boolVal);
    System.Console.WriteLine("{0} as a string is {1}"
,
        boolVal, stringVal);
}

C++

public:
   void ConvertStringBoolean( String^ stringVal )
   {
      bool boolVal = false;

      try
      {
         boolVal = System::Convert::ToBoolean( stringVal );
         if ( boolVal )
         {
            System::Console::WriteLine(
               "String was equal to System::Boolean::TrueString." );
         }
         else
         {
            System::Console::WriteLine(
               "String was equal to System::Boolean::FalseString." );
         }
      }
      catch ( System::FormatException^ ) 
      {
         System::Console::WriteLine( "The String must equal System::Boolean::TrueString
 " +
            "or System::Boolean::FalseString." );
      }
      
      // A conversion from bool to String will always succeed.
      stringVal = System::Convert::ToString( boolVal );
      System::Console::WriteLine( " {0} as a String is {1}",
         boolVal, stringVal );
   }

public void ConvertStringBoolean(String stringVal)
{
    boolean boolVal = false;

    try {        
        boolVal = System.Convert.ToBoolean(stringVal);
        if (boolVal) {            
            System.Console.WriteLine(
                "String was equal to System.Boolean.TrueString.");
        }
        else {            
            System.Console.WriteLine(
                "String was equal to System.Boolean.FalseString.");
        }
    }
    catch (System.FormatException exp) {        
        System.Console.WriteLine(
            ("The string must equal System.Boolean.TrueString
 "  
            + "or System.Boolean.FalseString."));
    }

    // A conversion from bool to string will always succeed.
    stringVal = System.Convert.ToString(boolVal);
    System.Console.WriteLine("{0} as a string is {1}"
, 
        System.Convert.ToString(boolVal), stringVal);
} //ConvertStringBoolean

プラットフォーム

バージョン情報

.NET Framework
サポート対象 : 2.0、1.1、1.0
.NET Compact Framework
サポート対象 : 2.0、1.0

参照

関連項目
Convert クラス
Convert メンバ
System 名前空間
String

Convert.ToBoolean メソッド (UInt32)

指定した 32 ビット符号なし整数の値を等価のブール値に変換します。

このメソッドは、CLS に準拠していません。

名前空間: System
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

<CLSCompliantAttribute(False)> _
Public Shared Function ToBoolean
 ( _
    value As UInteger _
) As Boolean

Visual Basic (使用法)

Dim value As UInteger
Dim returnValue As Boolean

returnValue = Convert.ToBoolean(value)

[CLSCompliantAttribute(false)] 
public static bool ToBoolean
 (
    uint value
)

C++

[CLSCompliantAttribute(false)] 
public:
static bool ToBoolean (
    unsigned int value
)

/** @attribute CLSCompliantAttribute(false) */ 
public static boolean ToBoolean (
    UInt32 value
)

JScript

CLSCompliantAttribute(false) 
public static function ToBoolean
 (
    value : uint
) : boolean

パラメータ

value: 32 ビット符号なし整数。

戻り値
value が 0 以外の場合は true。0 の場合は false。

プラットフォーム

バージョン情報

.NET Framework
サポート対象 : 2.0、1.1、1.0
.NET Compact Framework
サポート対象 : 2.0、1.0

参照

関連項目
Convert クラス
Convert メンバ
System 名前空間
UInt32

Convert.ToBoolean メソッド (DateTime)

このメソッドを呼び出すと、必ず InvalidCastException がスローされます。

名前空間: System
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

Public Shared Function ToBoolean
 ( _
    value As DateTime _
) As Boolean

Visual Basic (使用法)

Dim value As DateTime
Dim returnValue As Boolean

returnValue = Convert.ToBoolean(value)

public static bool ToBoolean
 (
    DateTime value
)

C++

public:
static bool ToBoolean (
    DateTime value
)

public static boolean ToBoolean (
    DateTime value
)

JScript

public static function ToBoolean
 (
    value : DateTime
) : boolean

パラメータ

value: DateTime。

戻り値
この変換はサポートされていません。値は返されません。

例外

例外の種類	条件
InvalidCastException	この変換はサポートされていません。

解説

このメソッドは、今後使用するために予約されています。

使用例

DateTime 値からブール値へ変換すると InvalidCastException がスローされるコード例を次に示します。

Visual Basic

Public Sub ConvertBoolean()
    Const year As Integer
 = 1979
    Const month As Integer
 = 7
    Const day As Integer
 = 28
    Const hour As Integer
 = 13
    Const minute As Integer
 = 26
    Const second As Integer
 = 15
    Const millisecond As Integer
 = 53

    Dim dateTime As New
 DateTime(year, month, day, hour, minute, _
                                 second, millisecond)

    Dim boolVal As Boolean

    ' System.InvalidCastException is always thrown.
    Try
        boolVal = System.Convert.ToBoolean(dateTime)
    Catch exception As System.InvalidCastException
        System.Console.WriteLine("Conversion from DateTime to
 " + _
                "Boolean is not supported by the framework.")
    End Try
End Sub

public void ConvertBoolean() {
    const int year            = 1979;
    const int month            = 7;   
    const int day            = 28;
    const int hour            = 13;
    const int minute        = 26;
    const int second        = 15;
    const int millisecond    = 53;

    DateTime dateTime = new DateTime(year, month, day, hour,
                                minute, second, millisecond);
    
    bool boolVal;

    // System.InvalidCastException is always thrown.
    try {
        boolVal = System.Convert.ToBoolean(dateTime);
    }
    catch (System.InvalidCastException) {
        System.Console.WriteLine("Conversion from DateTime to " +
            "Boolean is not supported by the framework.");
    }
}

C++

public:
   void ConvertBoolean()
   {
      const int year = 1979;
      const int month = 7;
      const int day = 28;
      const int hour = 13;
      const int minute = 26;
      const int second = 15;
      const int millisecond = 53;
      DateTime dateTime( year, month, day, hour,
         minute, second, millisecond );
      bool boolVal;
      
      // System::InvalidCastException is always thrown.
      try
      {
         boolVal = System::Convert::ToBoolean( dateTime );
      }
      catch ( System::InvalidCastException^ ) 
      {
         System::Console::WriteLine( "Conversion from DateTime to Boolean "+
            "is not supported by the framework." );
      }
   }

public void ConvertBoolean()
{
    final int year = 1979;
    final int month = 7;
    final int day = 28;
    final int hour = 13;
    final int minute = 26;
    final int second = 15;
    final int millisecond = 53;
    DateTime dateTime = new DateTime(year, month, day, hour, minute,
 second,
                            millisecond);
    boolean boolVal;

    // System.InvalidCastException is always thrown.
    try {        
        boolVal = System.Convert.ToBoolean(dateTime);
    }
    catch (System.InvalidCastException exp) {        
        System.Console.WriteLine(("Conversion from DateTime to "
            + "Boolean is not supported by the framework."));
    }
} //ConvertBoolean

プラットフォーム

バージョン情報

.NET Framework
サポート対象 : 2.0、1.1、1.0

参照

関連項目
Convert クラス
Convert メンバ
System 名前空間

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Convert.ToBoolean メソッドとは？わかりやすく解説

Convert.ToBoolean メソッド (UInt16)

Convert.ToBoolean メソッド (Char)

Convert.ToBoolean メソッド (Int32)

Convert.ToBoolean メソッド

関連項目

Convert.ToBoolean メソッド (Object, IFormatProvider)

Convert.ToBoolean メソッド

関連項目

Convert.ToBoolean メソッド (Int64)

Convert.ToBoolean メソッド (Object)

Convert.ToBoolean メソッド (Byte)

Convert.ToBoolean メソッド (String, IFormatProvider)

Convert.ToBoolean メソッド (SByte)

Convert.ToBoolean メソッド (Int16)

Convert.ToBoolean メソッド (Double)

Convert.ToBoolean メソッド (UInt64)

Convert.ToBoolean メソッド (Single)

Convert.ToBoolean メソッド (Decimal)

Convert.ToBoolean メソッド (Boolean)

Convert.ToBoolean メソッド (String)

Convert.ToBoolean メソッド (UInt32)

Convert.ToBoolean メソッド (DateTime)

「Convert.ToBoolean メソッド」の関連用語


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Convert.ToBoolean メソッドとは？ わかりやすく解説

Convert.ToBoolean メソッド (UInt16)

Convert.ToBoolean メソッド (Char)

Convert.ToBoolean メソッド (Int32)

Convert.ToBoolean メソッド

関連項目

Convert.ToBoolean メソッド (Object, IFormatProvider)

Convert.ToBoolean メソッド

関連項目

Convert.ToBoolean メソッド (Int64)

Convert.ToBoolean メソッド (Object)

Convert.ToBoolean メソッド (Byte)

Convert.ToBoolean メソッド (String, IFormatProvider)

Convert.ToBoolean メソッド (SByte)

Convert.ToBoolean メソッド (Int16)

Convert.ToBoolean メソッド (Double)

Convert.ToBoolean メソッド (UInt64)

Convert.ToBoolean メソッド (Single)

Convert.ToBoolean メソッド (Decimal)

Convert.ToBoolean メソッド (Boolean)

Convert.ToBoolean メソッド (String)

Convert.ToBoolean メソッド (UInt32)

Convert.ToBoolean メソッド (DateTime)

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「Convert.ToBoolean メソッド」の関連用語

Convert.ToBoolean メソッドとは？わかりやすく解説