Decimal.ToDouble メソッド

.NET Framework クラス ライブラリ リファレンス

Decimal.ToDouble メソッド

指定した Decimal の値を、それと等価の倍精度浮動小数点数に変換します。

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

Visual Basic (宣言)

Public Shared Function ToDouble
 ( _
    d As Decimal _
) As Double

Visual Basic (使用法)

Dim d As Decimal
Dim returnValue As Double

returnValue = Decimal.ToDouble(d)

C#

public static double ToDouble (
    decimal d
)

C++

public:
static double ToDouble (
    Decimal d
)

J#

public static double ToDouble (
    Decimal d
)

JScript

public static function ToDouble
 (
    d : decimal
) : double

パラメータ

d

変換する Decimal 値。

戻り値
d と等価の倍精度浮動小数点数。

解説

倍精度浮動小数点数の有効桁数が Decimal より少ないため、この演算によって丸め誤差が発生することがあります。

使用例

ToDouble メソッドを使用して、Decimal の数値を Double の値に変換するコード例を次に示します。

Visual Basic

' Example of the Decimal.ToSingle and Decimal.ToDouble methods.
Imports System
Imports Microsoft.VisualBasic

Module DecimalToSgl_DblDemo

    Dim formatter As String
 = "{0,30}{1,17}{2,23}"

    ' Convert the Decimal argument; no exceptions are thrown.
    Sub DecimalToSgl_Dbl( argument As Decimal
 )

        Dim SingleValue   As Object
        Dim DoubleValue   As Object

        ' Convert the argument to a Single value.
        SingleValue = Decimal.ToSingle( argument )

        ' Convert the argument to a Double value.
        DoubleValue = Decimal.ToDouble( argument )

        Console.WriteLine( formatter, argument, _
            SingleValue, DoubleValue )
    End Sub

    Sub Main( )

        Console.WriteLine( "This example of the "
 & vbCrLf & _
            "  Decimal.ToSingle( Decimal ) and " &
 vbCrLf & _
            "  Decimal.ToDouble( Decimal ) " &
 vbCrLf & "methods " & _
            "generates the following output. It "
 & vbCrLf & _
            "displays several converted Decimal values."
 & vbCrLf )
        Console.WriteLine( formatter, "Decimal argument",
 _
            "Single", "Double"
 )
        Console.WriteLine( formatter, "----------------",
 _
            "------", "------"
 )

        ' Convert Decimal values and display the results.
        DecimalToSgl_Dbl( 0.0000000000000000000000000001D )
        DecimalToSgl_Dbl( 0.0000000000112233445566778899D )
        DecimalToSgl_Dbl( 123D )
        DecimalToSgl_Dbl( New Decimal( 123000000,
 0, 0, False, 6 ) )
        DecimalToSgl_Dbl( 123456789.123456789D )
        DecimalToSgl_Dbl( 123456789123456789123456789D )
        DecimalToSgl_Dbl( Decimal.MinValue )
        DecimalToSgl_Dbl( Decimal.MaxValue )
    End Sub 
End Module 

' This example of the
'   Decimal.ToSingle( Decimal ) and
'   Decimal.ToDouble( Decimal )
' methods generates the following output. It
' displays several converted Decimal values.
' 
'               Decimal argument           Single                 Double
'               ----------------           ------                 ------
' 0.0000000000000000000000000001            1E-28                  1E-28
' 0.0000000000112233445566778899     1.122334E-11   1.12233445566779E-11
'                            123              123                  
  123
'                     123.000000              123                  
  123
'            123456789.123456789     1.234568E+08       123456789.123457
'    123456789123456789123456789     1.234568E+26   1.23456789123457E+26
' -79228162514264337593543950335    -7.922816E+28  -7.92281625142643E+28
'  79228162514264337593543950335     7.922816E+28   7.92281625142643E+28

C#

// Example of the decimal.ToSingle and decimal.ToDouble methods.
using System;

class DecimalToSgl_DblDemo
{
    static string formatter = "{0,30}{1
,17}{2,23}";

    // Convert the decimal argument; no exceptions are thrown.
    public static void DecimalToSgl_Dbl(
 decimal argument )
    {
        object SingleValue;
        object DoubleValue;

        // Convert the argument to a float value.
        SingleValue = decimal.ToSingle( argument );

        // Convert the argument to a double value.
        DoubleValue = decimal.ToDouble( argument );

        Console.WriteLine( formatter, argument, 
            SingleValue, DoubleValue );
    }

    public static void Main(
 )
    {
        Console.WriteLine( "This example of the \n" +
            "  decimal.ToSingle( decimal ) and \n" +
            "  decimal.ToDouble( decimal ) \nmethods " +
            "generates the following output. It \ndisplays " +
            "several converted decimal values.\n" );
        Console.WriteLine( formatter, "decimal argument", 
            "float", "double" );
        Console.WriteLine( formatter, "----------------", 
            "-----", "------" );

        // Convert decimal values and display the results.
        DecimalToSgl_Dbl( 0.0000000000000000000000000001M );
        DecimalToSgl_Dbl( 0.0000000000123456789123456789M );
        DecimalToSgl_Dbl( 123M );
        DecimalToSgl_Dbl( new decimal( 123000000, 0, 0, false,
 6 ) );
        DecimalToSgl_Dbl( 123456789.123456789M );
        DecimalToSgl_Dbl( 123456789123456789123456789M );
        DecimalToSgl_Dbl( decimal.MinValue );
        DecimalToSgl_Dbl( decimal.MaxValue );
    }
}

/*
This example of the
  decimal.ToSingle( decimal ) and
  decimal.ToDouble( decimal )
methods generates the following output. It
displays several converted decimal values.

              decimal argument            float              
   double
              ----------------            -----                 ------
0.0000000000000000000000000001            1E-28                  1E-28
0.0000000000123456789123456789     1.234568E-11   1.23456789123457E-11
                           123              123                    123
                    123.000000              123                    123
           123456789.123456789     1.234568E+08       123456789.123457
   123456789123456789123456789     1.234568E+26   1.23456789123457E+26
-79228162514264337593543950335    -7.922816E+28  -7.92281625142643E+28
 79228162514264337593543950335     7.922816E+28   7.92281625142643E+28
*/

C++

// Example of the Decimal::ToSingle and Decimal::ToDouble methods.
using namespace System;
#define formatter "{0,30}{1,17}{2,23}"

// Convert the Decimal argument; no exceptions are thrown.
void DecimalToSgl_Dbl( Decimal argument )
{
   Object^ SingleValue;
   Object^ DoubleValue;
   
   // Convert the argument to a float value.
   SingleValue = Decimal::ToSingle( argument );
   
   // Convert the argument to a double value.
   DoubleValue = Decimal::ToDouble( argument );
   Console::WriteLine( formatter, argument, SingleValue, DoubleValue );
}

int main()
{
   Console::WriteLine( "This example of the \n"
   "  Decimal::ToSingle( Decimal ) and \n"
   "  Decimal::ToDouble( Decimal ) \nmethods "
   "generates the following output. It \ndisplays "
   "several converted Decimal values.\n" );
   Console::WriteLine( formatter, "Decimal argument", "float",
 "double" );
   Console::WriteLine( formatter, "----------------", "-----",
 "------" );
   
   // Convert Decimal values and display the results.
   DecimalToSgl_Dbl( Decimal::Parse(  "0.0000000000000000000000000001"
 ) );
   DecimalToSgl_Dbl( Decimal::Parse(  "0.0000000000123456789123456789"
 ) );
   DecimalToSgl_Dbl( Decimal::Parse(  "123" ) );
   DecimalToSgl_Dbl( Decimal(123000000,0,0,false,6) );
   DecimalToSgl_Dbl( Decimal::Parse(  "123456789.123456789" ) );
   DecimalToSgl_Dbl( Decimal::Parse(  "123456789123456789123456789" ) );
   DecimalToSgl_Dbl( Decimal::MinValue );
   DecimalToSgl_Dbl( Decimal::MaxValue );
}

/*
This example of the
  Decimal::ToSingle( Decimal ) and
  Decimal::ToDouble( Decimal )
methods generates the following output. It
displays several converted Decimal values.

              Decimal argument            float              
   double
              ----------------            -----                 ------
0.0000000000000000000000000001            1E-28                  1E-28
0.0000000000123456789123456789     1.234568E-11   1.23456789123457E-11
                           123              123                    123
                    123.000000              123                    123
           123456789.123456789     1.234568E+08       123456789.123457
   123456789123456789123456789     1.234568E+26   1.23456789123457E+26
-79228162514264337593543950335    -7.922816E+28  -7.92281625142643E+28
 79228162514264337593543950335     7.922816E+28   7.92281625142643E+28
*/

J#

// Example of the decimal.ToSingle and decimal.ToDouble methods.
import System.* ;

class DecimalToSgl_DblDemo
{
    private static String formatter = "{0
,30}{1,17}{2,23}";
      
    // Convert the decimal argument; no exceptions are thrown.
    public static void DecimalToSgl_Dbl(System.Decimal
 argument) 
    {
        Object singleValue;
        Object doubleValue;
      
        // Convert the argument to a float value.
        singleValue = (System.Single)System.Decimal.ToSingle(argument);
          
        // Convert the argument to a double value.
        doubleValue = (System.Double)System.Decimal.ToDouble(argument);
        Console.WriteLine(formatter, argument, singleValue, doubleValue);
    }
      
    public static void main(String[]
 args)
    {
        Console.WriteLine("This example of the \n" 
            + "  decimal.ToSingle( decimal ) and \n" 
            + "  decimal.ToDouble( decimal ) \nmethods " 
            + "generates the following output. It \ndisplays " 
            + "several converted decimal values.\n");
        
        Console.WriteLine(formatter, "decimal argument", "float",
 "double");
        Console.WriteLine(formatter, "----------------", "-----",
 "------");
            
        // Convert decimal values and display the results.
        DecimalToSgl_Dbl(new System.Decimal(0.0000000000000000000000000001));
        DecimalToSgl_Dbl(new System.Decimal(0.0000000000123456789123456789));
        DecimalToSgl_Dbl(new System.Decimal(123));
        DecimalToSgl_Dbl(new System.Decimal(123000000, 0, 0, false,
 (ubyte)6));
        DecimalToSgl_Dbl(new System.Decimal(123456789.123456789));
        DecimalToSgl_Dbl(new System.Decimal(123456789123456789123456789F));
        DecimalToSgl_Dbl(System.Decimal.MinValue);
        DecimalToSgl_Dbl(System.Decimal.MaxValue);
    }
}

/*
This example of the
  decimal.ToSingle( decimal ) and
  decimal.ToDouble( decimal )
methods generates the following output. It
displays several converted decimal values.

              decimal argument            float              
   double
              ----------------            -----                 ------
0.0000000000000000000000000001            1E-28                  1E-28
   0.0000000000123456789123457     1.234568E-11   1.23456789123457E-11
                           123              123                    123
                    123.000000              123                    123
              123456789.123457     1.234568E+08       123456789.123457
   123456800000000000000000000     1.234568E+26           1.234568E+26
-79228162514264337593543950335    -7.922816E+28  -7.92281625142643E+28
 79228162514264337593543950335     7.922816E+28   7.92281625142643E+28
*/

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

関連項目
Decimal 構造体
Decimal メンバ
System 名前空間
Double