EncoderExceptionFallback EncoderExceptionFallback EncoderExceptionFallback EncoderExceptionFallback Class

定義

出力バイト シーケンスに変換できない入力文字のために、フォールバックと呼ばれるエラー処理機構を提供します。Provides a failure-handling mechanism, called a fallback, for an input character that cannot be converted to an output byte sequence. フォールバックは、入力文字を出力バイト シーケンスに変換できない場合に例外をスローします。The fallback throws an exception if an input character cannot be converted to an output byte sequence. このクラスは継承できません。This class cannot be inherited.

public ref class EncoderExceptionFallback sealed : System::Text::EncoderFallback
[System.Serializable]
public sealed class EncoderExceptionFallback : System.Text.EncoderFallback
type EncoderExceptionFallback = class
    inherit EncoderFallback
Public NotInheritable Class EncoderExceptionFallback
Inherits EncoderFallback
継承
EncoderExceptionFallbackEncoderExceptionFallbackEncoderExceptionFallbackEncoderExceptionFallback
属性

次のコード例に示します、EncoderExceptionFallbackEncoderFallbackExceptionクラス。The following code example demonstrates the EncoderExceptionFallback and EncoderFallbackException classes.

// This example demonstrates the EncoderExceptionFallback class.

using namespace System;
using namespace System::Text;

int main()
{
    // Create an encoding, which is equivalent to calling the
    // ASCIIEncoding class constructor.
    // The EncoderExceptionFallback parameter causes an exception to
    // be thrown when a character cannot be encoded.
    // A decoder exception fallback is also specified, but it is not
    // used because this example terminates during the encoding operation.

    Encoding^ asciiEncoding = Encoding::GetEncoding("us-ascii",
        gcnew EncoderExceptionFallback(), gcnew DecoderExceptionFallback());

    // The input string consists of the Unicode characters LEFT POINTING
    // DOUBLE ANGLE QUOTATION MARK (U+00AB), 'X' (U+0058), and RIGHT
    // POINTING DOUBLE ANGLE QUOTATION MARK (U+00BB).
    // The encoding can only encode characters in the US-ASCII range of
    // U+0000 through U+007F. Consequently, the characters bracketing the
    // 'X' character cause an exception.
    String^ inputString = L"\u00abX\u00bb";

    String^ twoNewLines = Environment::NewLine + Environment::NewLine;
    array<Byte>^ encodedBytes = gcnew array<Byte>(
        asciiEncoding->GetMaxByteCount(inputString->Length));
    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);

    // ---------------------------------------------------------------------
    // Attempt to encode the input string. However, an exception is thrown
    // before the input string can be encoded.

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

    // The code example terminates during the call to the GetBytes() method.
    try
    {
        numberOfEncodedBytes = asciiEncoding->GetBytes(inputString, 0,
            inputString->Length, encodedBytes, 0);
        // This statement is never executed.
        Console::WriteLine("This statement is never executed.");
    }
    catch (EncoderFallbackException^ 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): "X"
Input string in hexadecimal: 0xAB 0x58 0xBB

Encode the input string...
System.Text.EncoderFallbackException: Unable to translate Unicode character \u00AB at inde
x 0 to specified code page.
at System.Text.EncoderExceptionFallbackBuffer.Fallback(Char charUnknown, Int32 index)
at System.Text.EncoderFallbackBuffer.InternalFallback(Char ch, Char*& chars)
at System.Text.ASCIIEncoding.GetBytes(Char* chars, Int32 charCount, Byte* bytes, Int32
byteCount, EncoderNLS encoder)
at System.Text.ASCIIEncoding.GetBytes(String chars, Int32 charIndex, Int32 charCount, B
yte[] bytes, Int32 byteIndex)
at Sample.Main()

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

*/
// This example demonstrates the EncoderExceptionFallback 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 EncoderExceptionFallback parameter causes an exception to
// be thrown when a character cannot be encoded. 
// A decoder exception fallback is also specified, but it is not 
// used because this example terminates during the encoding operation.  

    Encoding ae = Encoding.GetEncoding(
                  "us-ascii",
                  new EncoderExceptionFallback(), 
                  new DecoderExceptionFallback());

// The input string consists of the Unicode characters LEFT POINTING 
// DOUBLE ANGLE QUOTATION MARK (U+00AB), 'X' (U+0058), and RIGHT POINTING 
// DOUBLE ANGLE QUOTATION MARK (U+00BB). 
// The encoding can only encode characters in the US-ASCII range of U+0000 
// through U+007F. Consequently, the characters bracketing the 'X' character
// cause an exception.
    string inputString = "\u00abX\u00bb";

    string twoNewLines = "\n\n";
    byte[] encodedBytes = new byte[ae.GetMaxByteCount(inputString.Length)];
    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);

// --------------------------------------------------------------------------
// Attempt to encode the input string. However, an exception is thrown before
// the input string can be encoded.

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

// The code example terminates during the call to the GetBytes() method.
    try {
        numberOfEncodedBytes = ae.GetBytes(inputString, 0, inputString.Length, 
                                           encodedBytes, 0);
        }
    catch (EncoderFallbackException e)
        {
        Console.WriteLine(e);
        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): "«X»"
Input string in hexadecimal: 0xAB 0x58 0xBB

Encode the input string...
System.Text.EncoderFallbackException: Unable to translate Unicode character \u00AB at inde
x 0 to specified code page.
   at System.Text.EncoderExceptionFallbackBuffer.Fallback(Char charUnknown, Int32 index)
   at System.Text.EncoderFallbackBuffer.InternalFallback(Char ch, Char*& chars)
   at System.Text.ASCIIEncoding.GetBytes(Char* chars, Int32 charCount, Byte* bytes, Int32
byteCount, EncoderNLS encoder)
   at System.Text.ASCIIEncoding.GetBytes(String chars, Int32 charIndex, Int32 charCount, B
yte[] bytes, Int32 byteIndex)
   at Sample.Main()

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

*/
' This example demonstrates the EncoderExceptionFallback 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 EncoderExceptionFallback parameter causes an exception to
        ' be thrown when a character cannot be encoded. 
        ' A decoder exception fallback is also specified, but it is not 
        ' used because this example terminates during the encoding operation.  


        Dim eef As New EncoderExceptionFallback()
        Dim def As New DecoderExceptionFallback()
        Dim ae As Encoding = Encoding.GetEncoding("us-ascii", eef, def)
        
        ' The input string consists of the Unicode characters LEFT POINTING 
        ' DOUBLE ANGLE QUOTATION MARK (U+00AB), 'X' (U+0058), and RIGHT POINTING 
        ' DOUBLE ANGLE QUOTATION MARK (U+00BB). 
        ' The encoding can only encode characters in the US-ASCII range of U+0000 
        ' through U+007F. Consequently, the characters bracketing the 'X' character
        ' cause an exception.

        Dim inputString As String = "«X»"
        
        Dim twoNewLines As String = vbCrLf & vbCrLf
        Dim numberOfEncodedBytes As Integer = ae.GetMaxByteCount(inputString.Length)
        ' 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)
        
        ' --------------------------------------------------------------------------
        ' Attempt to encode the input string. However, an exception is thrown before
        ' the input string can be encoded.
        Console.WriteLine("Encode the input string...")
        
        ' The code example terminates during the call to the GetBytes() method.
        Try
            numberOfEncodedBytes = ae.GetBytes(inputString, 0, inputString.Length, _
                                               encodedBytes, 0)
        Catch e As EncoderFallbackException
            Console.WriteLine(e)
            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): "X"
'Input string in hexadecimal: 0xAB 0x58 0xBB
'
'Encode the input string...
'System.Text.EncoderFallbackException: Unable to translate Unicode character \u00AB at inde
'x 0 to specified code page.
'   at System.Text.EncoderExceptionFallbackBuffer.Fallback(Char charUnknown, Int32 index)
'   at System.Text.EncoderFallbackBuffer.InternalFallback(Char ch, Char*& chars)
'   at System.Text.ASCIIEncoding.GetBytes(Char* chars, Int32 charCount, Byte* bytes, Int32
'byteCount, EncoderNLS encoder)
'   at System.Text.ASCIIEncoding.GetBytes(String chars, Int32 charIndex, Int32 charCount, B
'yte[] bytes, Int32 byteIndex)
'   at Sample.Main()
'
'*** THE CODE EXAMPLE TERMINATES HERE AS INTENDED. ***
'

注釈

Unicode 文字をまたは通信リンクを介して、ディスクなど、物理メディアに転送できる、その後のバイトでエンコードされたシーケンスにマップするエンコーディングします。An encoding maps a Unicode character to an encoded sequence of bytes, which can subsequently be transferred to a physical medium, such as a disk, or over a communications link. 文字をさまざまな方法でマップしてから派生した型で表される、特定のエンコード、Encodingクラス。Characters can be mapped in various ways, and a particular encoding is represented by a type derived from the Encoding class. 具体的には、エンコードの種類のGetBytesメソッドが、バイト シーケンスに文字をエンコードおよびGetCharsメソッドは、文字をバイト シーケンスをデコードします。Specifically, the encoding type's GetBytes method encodes a character to a byte sequence, and the GetChars method decodes a byte sequence to a character.

エンコード操作は、そのエンコードが入力文字を表すことができない場合に失敗します。An encoding operation can fail if the input character cannot be represented by the encoding. たとえば、ASCIIEncodingオブジェクトは、u+0000 U + 007F ~ が範囲外の Unicode コード ポイント値を生成する文字をエンコードことはできません。For example, a ASCIIEncoding object cannot encode a character that yields a Unicode code point value that is outside the range U+0000 to U+007F.

場合は、エンコードまたはデコード変換を実行することはできませんでは、.NET Framework は、フォールバックと呼ばれるエラー処理メカニズムを提供します。In cases where an encoding or decoding conversion cannot be performed, the .NET Framework provides a failure-handling mechanism called a fallback. アプリケーションで使用して定義済みの .NET Framework エンコーダー フォールバック、またはから派生したカスタムのエンコーダー フォールバックを作成することができます、EncoderFallbackEncoderFallbackBufferクラス。Your application can use the predefined .NET Framework encoder fallback, or it can create a custom encoder fallback derived from the EncoderFallback and EncoderFallbackBuffer classes.

.NET Framework では、エンコーディングの変換エラーを処理するための別のフォールバック ストラテジを実装する 2 つの定義済みクラスを提供します。The .NET Framework provides two predefined classes that implement different fallback strategies for handling encoding conversion failures. EncoderReplacementFallbackクラスには、任意の入力を変換できない文字の文字列が置換されます。The EncoderReplacementFallback class substitutes a string provided for any input character that cannot be converted. 代替文字列は、無効な文字の代わりにエンコードされ、エンコード処理は引き続き、残りの入力を変換します。The substitute string is encoded in place of the invalid character, and then the encoding operation continues converting the remainder of the input. これに対し、EncoderExceptionFallbackクラスがスローされます、EncoderFallbackExceptionに無効な文字が発生したとき。In contrast, the EncoderExceptionFallback class throws a EncoderFallbackException when an invalid character is encountered.

コンストラクター

EncoderExceptionFallback() EncoderExceptionFallback() EncoderExceptionFallback() EncoderExceptionFallback()

EncoderExceptionFallback クラスの新しいインスタンスを初期化します。Initializes a new instance of the EncoderExceptionFallback class.

プロパティ

MaxCharCount MaxCharCount MaxCharCount MaxCharCount

このインスタンスが返すことができる最大文字数を取得します。Gets the maximum number of characters this instance can return.

メソッド

CreateFallbackBuffer() CreateFallbackBuffer() CreateFallbackBuffer() CreateFallbackBuffer()

文字シーケンスをバイト シーケンスに変換できない場合は、例外をスローするエンコーダー フォールバック バッファーを返します。Returns an encoder fallback buffer that throws an exception if it cannot convert a character sequence to a byte sequence.

Equals(Object) Equals(Object) Equals(Object) Equals(Object)

現在の EncoderExceptionFallback オブジェクトと指定したオブジェクトが等しいかどうかを示します。Indicates whether the current EncoderExceptionFallback object and a specified object are equal.

GetHashCode() GetHashCode() GetHashCode() GetHashCode()

このインスタンスのハッシュ コードを取得します。Retrieves the hash code for this instance.

GetType() GetType() GetType() GetType()

現在のインスタンスの Type を取得します。Gets the Type of the current instance.

(Inherited from Object)
MemberwiseClone() MemberwiseClone() MemberwiseClone() MemberwiseClone()

現在の Object の簡易コピーを作成します。Creates a shallow copy of the current Object.

(Inherited from Object)
ToString() ToString() ToString() ToString()

現在のオブジェクトを表す文字列を返します。Returns a string that represents the current object.

(Inherited from Object)

適用対象

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