DecoderFallbackException クラス

.NET Framework クラス ライブラリ リファレンス

DecoderFallbackException クラス

メモ : このクラスは、.NET Framework version 2.0 で新しく追加されたものです。

デコーダ フォールバック操作が失敗したときにスローされる例外。このクラスは継承できません。

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

Visual Basic (宣言)

<SerializableAttribute> _
Public NotInheritable Class
 DecoderFallbackException
    Inherits ArgumentException

Visual Basic (使用法)

Dim instance As DecoderFallbackException

C#

[SerializableAttribute] 
public sealed class DecoderFallbackException
 : ArgumentException

C++

[SerializableAttribute] 
public ref class DecoderFallbackException sealed
 : public ArgumentException

J#

/** @attribute SerializableAttribute() */ 
public final class DecoderFallbackException
 extends ArgumentException

JScript

SerializableAttribute 
public final class DecoderFallbackException
 extends ArgumentException

使用例

DecoderExceptionFallback クラスと DecoderFallbackException クラスのコード例を次に示します。

Visual Basic

' This example demonstrates the DecoderExceptionFallback class.
Imports System
Imports System.Text

Class Sample
    Public Shared Sub Main()
 
        
        ' Create an encoding, which is equivalent to calling the 
        ' ASCIIEncoding class constructor. 
        ' The DecoderExceptionFallback parameter specifies that an exception
        ' is thrown if a character cannot be encoded. 
        ' An encoder exception fallback is also specified, but in this
 code
        ' example the encoding operation cannot fail.  


        Dim eef As New EncoderExceptionFallback()
        Dim def As New DecoderExceptionFallback()
        Dim ae As Encoding = Encoding.GetEncoding("us-ascii",
 eef, def)
        Dim inputString As String
 = "XYZ"
        Dim decodedString As String
        Dim twoNewLines As String
 = vbCrLf & vbCrLf
        Dim numberOfEncodedBytes As Integer
 = ae.GetByteCount(inputString)
        ' Counteract the compiler adding an extra element.
        Dim encodedBytes(numberOfEncodedBytes - 1) As
 Byte
        
        ' --------------------------------------------------------------------------
        Console.Clear()
        
        ' Display the name of the encoding.
        Console.WriteLine("The name of the encoding is ""{0}""."
 & vbCrLf, ae.WebName)
        
        ' Display the input string in text.
        Console.WriteLine("Input string ({0} characters): ""{1}""",
 inputString.Length, inputString)
        
        ' Display the input string in hexadecimal.
        ' Each element is converted to an integer with Convert.ToInt32.
        Console.Write("Input string in hexadecimal: ")
        Dim c As Char
        For Each c In  inputString.ToCharArray()
            Console.Write("0x{0:X2} ", Convert.ToInt32(c))
        Next c
        Console.Write(twoNewLines)
        
        ' --------------------------------------------------------------------------
        ' Encode the input string. 
        Console.WriteLine("Encode the input string...")
        numberOfEncodedBytes = ae.GetBytes(inputString, 0, inputString.Length, _
                                           encodedBytes, 0)
        ' Display the encoded bytes.
        ' Each element is converted to an integer with Convert.ToInt32.
        Console.WriteLine("Encoded bytes in hexadecimal ({0} bytes):"
 & vbCrLf, _
                           numberOfEncodedBytes)
        Dim b As Byte
        For Each b In  encodedBytes
            Console.Write("0x{0:X2} ", Convert.ToInt32(b))
        Next b
        Console.Write(twoNewLines)
        
        ' --------------------------------------------------------------------------
        ' Replace the encoded byte sequences for the characters 'X'
 and 'Z' with the 
        ' value 0xFF, which is outside the valid range of 0x00 to 0x7F
 for 
        ' ASCIIEncoding. The resulting byte sequence is actually the
 beginning of 
        ' this code example because it is the input to the decoder operation,
 and 
        ' is equivalent to a corrupted or improperly encoded byte sequence.
 

        encodedBytes(0) = &HFF
        encodedBytes(2) = &HFF
        
        Console.WriteLine("Display the corrupted byte sequence...")
        ' Each element is converted to an integer with Convert.ToInt32.
        Console.WriteLine("Encoded bytes in hexadecimal ({0} bytes):"
 & vbCrLf, _
                           numberOfEncodedBytes)
        For Each b In  encodedBytes
            Console.Write("0x{0:X2} ", Convert.ToInt32(b))
        Next b
        Console.Write(twoNewLines)
        
        ' --------------------------------------------------------------------------
        ' Attempt to decode the encoded bytes. However, an exception
 is thrown 
        ' before the byte sequence can be decoded.
        Console.WriteLine("Compare the decoded bytes to the input
 string...")
        
        Try
            decodedString = ae.GetString(encodedBytes)
        Catch dfe As DecoderFallbackException
            Console.WriteLine(dfe)
            Console.WriteLine(vbCrLf & _
                              "*** THE CODE EXAMPLE TERMINATES
 HERE AS INTENDED. ***")
            Return
        End Try
        
        ' This statement is never executed.
        Console.WriteLine("This statement is never executed.")
    
    End Sub 'Main
End Class 'Sample
'
'This code example produces the following results:
'
'The name of the encoding is "us-ascii".
'
'Input string (3 characters): "XYZ"
'Input string in hexadecimal: 0x58 0x59 0x5A
'
'Encode the input string...
'Encoded bytes in hexadecimal (3 bytes):
'
'0x58 0x59 0x5A
'
'Display the corrupted byte sequence...
'Encoded bytes in hexadecimal (3 bytes):
'
'0xFF 0x59 0xFF
'
'Compare the decoded bytes to the input string...
'System.Text.DecoderFallbackException: Unable to translate bytes [FF]
 at index 0 from speci
'fied code page to Unicode.
'   at System.Text.DecoderExceptionFallbackBuffer.Throw(Byte[] bytesUnknown,
 Int32 index)
'   at System.Text.DecoderExceptionFallbackBuffer.Fallback(Byte[] bytesUnknown,
 Int32 index
')
'   at System.Text.DecoderFallbackBuffer.InternalFallback(Byte[] bytes,
 Byte* pBytes)
'   at System.Text.ASCIIEncoding.GetCharCount(Byte* bytes, Int32 count,
 DecoderNLS decoder)
'
'   at System.String.CreateStringFromEncoding(Byte* bytes, Int32 byteLength,
 Encoding encod
'ing)
'   at System.Text.ASCIIEncoding.GetString(Byte[] bytes, Int32 byteIndex,
 Int32 byteCount)
'   at System.Text.Encoding.GetString(Byte[] bytes)
'   at Sample.Main()
'
'*** THE CODE EXAMPLE TERMINATES HERE AS INTENDED. ***
'
'

C#

// This example demonstrates the DecoderExceptionFallback class.

using System;
using System.Text;

class Sample 
{
    public static void Main()
 
    {

// Create an encoding, which is equivalent to calling the 
// ASCIIEncoding class constructor. 
// The DecoderExceptionFallback parameter specifies that an exception
// is thrown if a character cannot be encoded. 
// An encoder exception fallback is also specified, but in this code
// example the encoding operation cannot fail.  

    Encoding ae = Encoding.GetEncoding(
                  "us-ascii",
                  new EncoderExceptionFallback(), 
                  new DecoderExceptionFallback());
    string inputString = "XYZ";
    string decodedString;
    string twoNewLines = "\n\n";
    byte[] encodedBytes = new byte[ae.GetByteCount(inputString)];
    int numberOfEncodedBytes = 0;

// --------------------------------------------------------------------------
    Console.Clear();

// Display the name of the encoding.
    Console.WriteLine("The name of the encoding is \"{0}\".\n",
 ae.WebName);

// Display the input string in text.
    Console.WriteLine("Input string ({0} characters): \"{1}\"",
 
                       inputString.Length, inputString);

// Display the input string in hexadecimal.
    Console.Write("Input string in hexadecimal:
 ");
    foreach (char c in inputString.ToCharArray())
 
        {
        Console.Write("0x{0:X2} ", (int)c);
        }
    Console.Write(twoNewLines);

// --------------------------------------------------------------------------
// Encode the input string. 

    Console.WriteLine("Encode the input string...");
    numberOfEncodedBytes = ae.GetBytes(inputString, 0, inputString.Length, 
                                       encodedBytes, 0);
// Display the encoded bytes.
    Console.WriteLine("Encoded bytes in hexadecimal ({0}
 bytes):\n", 
                       numberOfEncodedBytes);
    foreach (byte b in encodedBytes)
        {
        Console.Write("0x{0:X2} ", (int)b);
        }
    Console.Write(twoNewLines);

// --------------------------------------------------------------------------

// Replace the encoded byte sequences for the characters 'X' and 'Z'
 with the 
// value 0xFF, which is outside the valid range of 0x00 to 0x7F for
 
// ASCIIEncoding. The resulting byte sequence is actually the beginning
 of 
// this code example because it is the input to the decoder operation,
 and 
// is equivalent to a corrupted or improperly encoded byte sequence.
 

    encodedBytes[0] = 0xFF;
    encodedBytes[2] = 0xFF;

    Console.WriteLine("Display the corrupted byte sequence...");
    Console.WriteLine("Encoded bytes in hexadecimal ({0}
 bytes):\n", 
                       numberOfEncodedBytes);
    foreach (byte b in encodedBytes)
        {
        Console.Write("0x{0:X2} ", (int)b);
        }
    Console.Write(twoNewLines);

// --------------------------------------------------------------------------
// Attempt to decode the encoded bytes. However, an exception is thrown
 
// before the byte sequence can be decoded.

    Console.WriteLine("Compare the decoded bytes to the input string...");

    try {
        decodedString = ae.GetString(encodedBytes);
        }
    catch (DecoderFallbackException dfe)
        {
        Console.WriteLine(dfe);
        Console.WriteLine("\n*** THE CODE EXAMPLE TERMINATES HERE AS INTENDED.
 ***");
        return;
        }

// This statement is never executed.
    Console.WriteLine("This statement is never executed.");
    }
}
/*
This code example produces the following results:

The name of the encoding is "us-ascii".

Input string (3 characters): "XYZ"
Input string in hexadecimal: 0x58 0x59 0x5A

Encode the input string...
Encoded bytes in hexadecimal (3 bytes):

0x58 0x59 0x5A

Display the corrupted byte sequence...
Encoded bytes in hexadecimal (3 bytes):

0xFF 0x59 0xFF

Compare the decoded bytes to the input string...
System.Text.DecoderFallbackException: Unable to translate bytes [FF] at index 0 from
 speci
fied code page to Unicode.
   at System.Text.DecoderExceptionFallbackBuffer.Throw(Byte[] bytesUnknown, Int32
 index)
   at System.Text.DecoderExceptionFallbackBuffer.Fallback(Byte[] bytesUnknown, Int32
 index
)
   at System.Text.DecoderFallbackBuffer.InternalFallback(Byte[] bytes, Byte* pBytes)
   at System.Text.ASCIIEncoding.GetCharCount(Byte* bytes, Int32 count, DecoderNLS
 decoder)

   at System.String.CreateStringFromEncoding(Byte* bytes, Int32 byteLength, Encoding
 encod
ing)
   at System.Text.ASCIIEncoding.GetString(Byte[] bytes, Int32 byteIndex, Int32 byteCount)
   at System.Text.Encoding.GetString(Byte[] bytes)
   at Sample.Main()

*** THE CODE EXAMPLE TERMINATES HERE AS INTENDED. ***

*/

C++

// This example demonstrates the DecoderExceptionFallback class.

using namespace System;
using namespace System::Text;

int main()
{
    // Create an encoding, which is equivalent to calling the
    // ASCIIEncoding class constructor.
    // The DecoderExceptionFallback parameter specifies that an exception
    // is thrown if a character cannot be encoded.
    // An encoder exception fallback is also specified, but in this
 code
    // example the encoding operation cannot fail.

    Encoding^ asciiEncoding = Encoding::GetEncoding("us-ascii",
        gcnew EncoderExceptionFallback(), gcnew DecoderExceptionFallback());
    String^ inputString = "XYZ";
    String^ decodedString;
    String^ twoNewLines = Environment::NewLine + Environment::NewLine ;

    array<Byte>^ encodedBytes = 
        gcnew array<Byte>(asciiEncoding->GetByteCount(inputString));
    int numberOfEncodedBytes = 0;

    // ---------------------------------------------------------------------
    Console::Clear();

    // Display the name of the encoding.
    Console::WriteLine("The name of the encoding is \"{0}\".{1}"
,
        asciiEncoding->WebName, Environment::NewLine);

    // Display the input string in text.
    Console::WriteLine("Input string ({0} characters): \"{1}\""
,
        inputString->Length, inputString);

    // Display the input string in hexadecimal.
    Console::Write("Input string in hexadecimal:
 ");
    for each (char c in
 inputString)
    {
        Console::Write("0x{0:X2} ", c);
    }
    Console::Write(twoNewLines);

    // ---------------------------------------------------------------------
    // Encode the input string.

    Console::WriteLine("Encode the input string...");

    numberOfEncodedBytes = asciiEncoding->GetBytes(inputString, 0,
        inputString->Length, encodedBytes, 0);

    // Display the encoded bytes.
    Console::WriteLine("Encoded bytes in hexadecimal ({0}
 bytes):{1}",
        numberOfEncodedBytes, Environment::NewLine);
    for each (Byte b in encodedBytes)
    {
        Console::Write("0x{0:X2} ", b);
    }
    Console::Write(twoNewLines);

    // ---------------------------------------------------------------------

    // Replace the encoded byte sequences for the characters 'X' and
 'Z'
    // with the value 0xFF, which is outside the valid range of 0x00
 to 0x7F
    // for ASCIIEncoding. The resulting byte sequence is actually the
    // beginning of this code example because it is the input to the
 decoder
    // operation, and is equivalent to a corrupted or improperly encoded
    // byte sequence.

    encodedBytes[0] = 0xFF;
    encodedBytes[2] = 0xFF;

    Console::WriteLine("Display the corrupted byte sequence...");
    Console::WriteLine("Encoded bytes in hexadecimal ({0}
 bytes):{1}",
        numberOfEncodedBytes, Environment::NewLine);
    for each (Byte b in encodedBytes)
    {
        Console::Write("0x{0:X2} ", b);
    }
    Console::Write(twoNewLines);

    // ---------------------------------------------------------------------
    // Attempt to decode the encoded bytes. However, an exception is
 thrown
    // before the byte sequence can be decoded.

    Console::WriteLine("Compare the decoded bytes to the input string...");

    try
    {
        decodedString = asciiEncoding->GetString(encodedBytes);
        // This statement is never executed.
        Console::WriteLine("This statement is never executed.");
    }
    catch (DecoderFallbackException^ ex)
    {
        Console::WriteLine(ex);
        Console::WriteLine(
            "{0}*** THE CODE EXAMPLE TERMINATES HERE AS INTENDED. ***",
 
            Environment::NewLine);
    }
}


/*
This code example produces the following results:

The name of the encoding is "us-ascii".

Input string (3 characters): "XYZ"
Input string in hexadecimal: 0x58 0x59 0x5A

Encode the input string...
Encoded bytes in hexadecimal (3 bytes):

0x58 0x59 0x5A

Display the corrupted byte sequence...
Encoded bytes in hexadecimal (3 bytes):

0xFF 0x59 0xFF

Compare the decoded bytes to the input string...
System.Text.DecoderFallbackException: Unable to translate bytes [FF] at index 0 from
 speci
fied code page to Unicode.
at System.Text.DecoderExceptionFallbackBuffer.Throw(Byte[] bytesUnknown, Int32 index)
at System.Text.DecoderExceptionFallbackBuffer.Fallback(Byte[] bytesUnknown, Int32
 index
)
at System.Text.DecoderFallbackBuffer.InternalFallback(Byte[] bytes, Byte* pBytes)
at System.Text.ASCIIEncoding.GetCharCount(Byte* bytes, Int32 count, DecoderNLS decoder)

at System.String.CreateStringFromEncoding(Byte* bytes, Int32 byteLength, Encoding
 encod
ing)
at System.Text.ASCIIEncoding.GetString(Byte[] bytes, Int32 byteIndex, Int32 byteCount)
at System.Text.Encoding.GetString(Byte[] bytes)
at Sample.Main()

*** THE CODE EXAMPLE TERMINATES HERE AS INTENDED. ***

*/

継承階層

System.Object
   System.Exception
     System.SystemException
       System.ArgumentException
        System.Text.DecoderFallbackException

スレッド セーフ

この型の public static (Visual Basic では Shared) メンバはすべて、スレッド セーフです。インスタンス メンバの場合は、スレッド セーフであるとは限りません。

プラットフォーム

Windows 98, Windows 2000 SP4, Windows Millennium Edition, 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

参照

関連項目
DecoderFallbackException メンバ
System.Text 名前空間
DecoderFallback クラス
DecoderExceptionFallback クラス