EncoderReplacementFallback クラス

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. フォールバックでは、元の入力文字の代わりに、ユーザー指定の置換文字列を使用します。The fallback uses a user-specified replacement string instead of the original input character. このクラスは継承できません。This class cannot be inherited.

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

クラスの例を次に示し EncoderReplacementFallback ます。The following example demonstrates the EncoderReplacementFallback class.

// This example demonstrates the EncoderReplacementFallback class.

using namespace System;
using namespace System::Text;

int main()
{
    // Create an encoding, which is equivalent to calling the
    // ASCIIEncoding class constructor.
    // The EncoderReplacementFallback parameter specifies that the
    // string, "(unknown)", replace characters that cannot be encoded.
    // A decoder replacement fallback is also specified, but in this
    // code example the decoding operation cannot fail.

    Encoding^ ascii = Encoding::GetEncoding("us-ascii",
        gcnew EncoderReplacementFallback("(unknown)"),
        gcnew DecoderReplacementFallback("(error)"));

    // 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 are replaced with the fallback replacement string,
    // "(unknown)".

    String^ inputString = "\u00abX\u00bb";
    String^ decodedString;
    String^ twoNewLines = Environment::NewLine + Environment::NewLine;
    array <Byte>^ encodedBytes = 
        gcnew array<Byte>(ascii->GetByteCount(inputString));
    int numberOfEncodedBytes = 0;

    // ---------------------------------------------------------------------
        // Display the name of the encoding.
    Console::WriteLine("The name of the encoding is \"{0}\".{1}", 
        ascii->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 = ascii->GetBytes(inputString, 0, inputString->Length,
        encodedBytes, 0);

    // Display the encoded bytes.
    Console::WriteLine("Encoded bytes in hexadecimal ({0} bytes):{1}",
        numberOfEncodedBytes, Environment::NewLine);
    for(int i = 0; i < encodedBytes->Length; i++)
    {
        Console::Write("0x{0:X2} ", encodedBytes[i]);
        if(((i + 1) % 6) == 0)
        {
            Console::WriteLine();
        }
    }
    Console::Write(twoNewLines);

    // ---------------------------------------------------------------------
    // Decode the encoded bytes, yielding a reconstituted string.

    Console::WriteLine("Decode the encoded bytes...");
    decodedString = ascii->GetString(encodedBytes);

    // Display the input string and the decoded string for comparison.
    Console::WriteLine("Input string:  \"{0}\"", inputString);
    Console::WriteLine("Decoded string:\"{0}\"", decodedString);
}



/*
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...
Encoded bytes in hexadecimal (19 bytes):

0x28 0x75 0x6E 0x6B 0x6E 0x6F
0x77 0x6E 0x29 0x58 0x28 0x75
0x6E 0x6B 0x6E 0x6F 0x77 0x6E
0x29

Decode the encoded bytes...
Input string:  "X"
Decoded string:"(unknown)X(unknown)"

*/
// This example demonstrates the EncoderReplacementFallback 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 EncoderReplacementFallback parameter specifies that the
// string, "(unknown)", replace characters that cannot be encoded.
// A decoder replacement fallback is also specified, but in this
// code example the decoding operation cannot fail.

    Encoding ae = Encoding.GetEncoding(
                  "us-ascii",
                  new EncoderReplacementFallback("(unknown)"),
                  new DecoderReplacementFallback("(error)"));

// 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
// are replaced with the fallback replacement string, "(unknown)".

    string inputString = "\u00abX\u00bb";
    string decodedString;
    string twoNewLines = "\n\n";
    byte[] encodedBytes = new byte[ae.GetByteCount(inputString)];
    int numberOfEncodedBytes = 0;
    int ix = 0;

// --------------------------------------------------------------------------
// 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);
    ix = 0;
    foreach (byte b in encodedBytes)
        {
        Console.Write("0x{0:X2} ", (int)b);
        ix++;
        if (0 == ix % 6) Console.WriteLine();
        }
    Console.Write(twoNewLines);

// --------------------------------------------------------------------------
// Decode the encoded bytes, yielding a reconstituted string.

    Console.WriteLine("Decode the encoded bytes...");
    decodedString = ae.GetString(encodedBytes);

// Display the input string and the decoded string for comparison.
    Console.WriteLine("Input string:  \"{0}\"", inputString);
    Console.WriteLine("Decoded string:\"{0}\"", decodedString);
    }
}
/*
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...
Encoded bytes in hexadecimal (19 bytes):

0x28 0x75 0x6E 0x6B 0x6E 0x6F
0x77 0x6E 0x29 0x58 0x28 0x75
0x6E 0x6B 0x6E 0x6F 0x77 0x6E
0x29

Decode the encoded bytes...
Input string:  "«X»"
Decoded string:"(unknown)X(unknown)"

*/
' This example demonstrates the EncoderReplacementFallback class.
Imports System.Text

Class Sample
    Public Shared Sub Main() 
        
        ' Create an encoding, which is equivalent to calling the 
        ' ASCIIEncoding class constructor. 
        ' The EncoderReplacementFallback parameter specifies that the 
        ' string, "(unknown)", replace characters that cannot be encoded. 
        ' A decoder replacement fallback is also specified, but in this 
        ' code example the decoding operation cannot fail.  

        Dim erf As New EncoderReplacementFallback("(unknown)")
        Dim drf As New DecoderReplacementFallback("(error)")
        Dim ae As Encoding = Encoding.GetEncoding("us-ascii", erf, drf)
        
        ' 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
        ' are replaced with the fallback replacement string, "(unknown)".

        Dim inputString As String = "«X»"
        Dim decodedString As String
        Dim twoNewLines As String = vbCrLf & vbCrLf
        Dim ix As Integer = 0
        Dim numberOfEncodedBytes As Integer = ae.GetByteCount(inputString)
        ' Counteract the compiler adding an extra byte to the array.
        Dim encodedBytes(numberOfEncodedBytes - 1) As Byte
        
        ' --------------------------------------------------------------------------
        ' 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)
        ix = 0
        Dim b As Byte
        For Each b In encodedBytes
            Console.Write("0x{0:X2} ", Convert.ToInt32(b))
            ix += 1
            If 0 = ix Mod 6 Then
                Console.WriteLine()
            End If
        Next b
        Console.Write(twoNewLines)
        
        ' --------------------------------------------------------------------------
        ' Decode the encoded bytes, yielding a reconstituted string.
        Console.WriteLine("Decode the encoded bytes...")
        decodedString = ae.GetString(encodedBytes)
        
        ' Display the input string and the decoded string for comparison.
        Console.WriteLine("Input string:  ""{0}""", inputString)
        Console.WriteLine("Decoded string:""{0}""", decodedString)
    
    End Sub
End Class
'
'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...
'Encoded bytes in hexadecimal (19 bytes):
'
'0x28 0x75 0x6E 0x6B 0x6E 0x6F
'0x77 0x6E 0x29 0x58 0x28 0x75
'0x6E 0x6B 0x6E 0x6F 0x77 0x6E
'0x29
'
'Decode the encoded bytes...
'Input string:  "X"
'Decoded string:"(unknown)X(unknown)"
'

注釈

エンコード操作またはデコード操作が失敗する一般的な理由は、基になるエンコーディングクラスが文字とそれに相当するバイトシーケンスとの間のマッピングを提供しない場合です。A common reason for an encoding or decoding operation to fail is if the underlying encoding class does not provide a mapping between a character and an equivalent byte sequence. たとえば、オブジェクトは、 ASCIIEncoding u + 0000 ~ u + 007F の範囲外の Unicode コードポイント値を持つ文字をエンコードすることはできません。For example, an ASCIIEncoding object cannot encode a character having a Unicode code point value that is outside the range U+0000 to U+007F. 入力文字を出力バイトシーケンスに変換できない場合、オブジェクトは、 EncoderReplacementFallback 元の入力文字に対して指定された置換文字列を置換します。If the input character cannot be converted to an output byte sequence, a EncoderReplacementFallback object substitutes a specified replacement string for the original input character. 変換処理では、置換文字列をエンコードしてから、元の入力の残りの部分を処理し続けます。The conversion process encodes the replacement string and then continues to process the remainder of the original input.

オブジェクトによって使用される置換文字列 EncoderReplacementFallback は、そのクラスコンストラクターの呼び出しによって決定されます。The replacement string used by an EncoderReplacementFallback object is determined by the call to its class constructor. 次の 2 つのオプションを使用できます。Two options are available:

  • 既定の文字に置き換えます。Replacement with the default character. コンストラクターを呼び出すと EncoderReplacementFallback() 、置換文字は "?" になります。(U + 003F)。If you call the EncoderReplacementFallback() constructor, the replacement character is "?" (U+003F).

  • 任意の文字列で置き換えます。Replacement with a string of your choice. コンストラクターを呼び出す場合は、 EncoderReplacementFallback(String) 置換後の文字列を指定します。If you call the EncoderReplacementFallback(String) constructor, you provide the replacement string.

このクラスで使用するフォールバック文字列を選択する場合は、文字列が、ターゲットエンコードでエンコードできる文字だけで構成されていることを確認してください。If you choose a fallback string to use with this class, make sure that the string is composed entirely of characters that can be encoded in the target encoding. それ以外の場合は、再帰フォールバックの結果としてが発生 ArgumentException します。Otherwise, a recursive fallback results, causing an ArgumentException.

このクラスは、エンコード変換エラーを処理するためのさまざまなフォールバックストラテジを実装する2つの .NET Framework クラスのうちの1つです。This class is one of two .NET Framework classes that implement different fallback strategies for handling encoding conversion failures. もう1つのクラスはクラスであり、 EncoderExceptionFallback EncoderFallbackException 無効な文字が検出された場合にをスローします。The other class is the EncoderExceptionFallback class, which throws an EncoderFallbackException when an invalid character is encountered.

コンストラクター

EncoderReplacementFallback()

EncoderReplacementFallback 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 EncoderReplacementFallback class.

EncoderReplacementFallback(String)

指定した置換文字列を使用して、EncoderReplacementFallback 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 EncoderReplacementFallback class using a specified replacement string.

プロパティ

DefaultString

EncoderReplacementFallback オブジェクトの値である置換文字列を取得します。Gets the replacement string that is the value of the EncoderReplacementFallback object.

MaxCharCount

EncoderReplacementFallback オブジェクトの置換文字列に含まれる文字数を取得します。Gets the number of characters in the replacement string for the EncoderReplacementFallback object.

メソッド

CreateFallbackBuffer()

この EncoderFallbackBuffer オブジェクトの置換文字列で初期化される EncoderReplacementFallback オブジェクトを作成します。Creates a EncoderFallbackBuffer object that is initialized with the replacement string of this EncoderReplacementFallback object.

Equals(Object)

指定したオブジェクトの値が、EncoderReplacementFallback オブジェクトと等しいかどうかを示します。Indicates whether the value of a specified object is equal to the EncoderReplacementFallback object.

GetHashCode()

EncoderReplacementFallback オブジェクトの値のハッシュ コードを取得します。Retrieves the hash code for the value of the EncoderReplacementFallback object.

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.

(継承元 Object)
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.

(継承元 Object)
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.

(継承元 Object)

適用対象

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