EncoderReplacementFallback Klasa

Definicja

Zapewnia mechanizm obsługi niepowodzeń o nazwie Fallback dla znaku wejściowego, którego nie można przekonwertować na sekwencję bajtów wyjściowych.Provides a failure handling mechanism, called a fallback, for an input character that cannot be converted to an output byte sequence. Funkcja Fallback używa ciągu zastępczego określonego przez użytkownika zamiast oryginalnego znaku wejściowego.The fallback uses a user-specified replacement string instead of the original input character. Klasa ta nie może być dziedziczona.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
Dziedziczenie
EncoderReplacementFallback
Atrybuty

Przykłady

Poniższy przykład demonstruje EncoderReplacementFallback klasę.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)"
'

Uwagi

Typową przyczyną niepowodzenia operacji kodowania lub dekodowania jest to, czy bazowa Klasa kodowania nie oferuje mapowania między znakiem a równoważną sekwencją bajtów.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. Na przykład ASCIIEncoding obiekt nie może kodować znaku mającego wartość punktu kodu Unicode, która znajduje się poza zakresem u + 0000 do u + 007F.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. Jeśli nie można przekonwertować znaku wejściowego na sekwencję bajtów wyjściowych, EncoderReplacementFallback obiekt zastępuje określony ciąg zastępczy dla oryginalnego znaku wejściowego.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. Proces konwersji koduje ciąg zamienny, a następnie kontynuuje przetwarzanie pozostałej części pierwotnych danych wejściowych.The conversion process encodes the replacement string and then continues to process the remainder of the original input.

Ciąg zamienny używany przez EncoderReplacementFallback obiekt jest określany przez wywołanie do jego konstruktora klasy.The replacement string used by an EncoderReplacementFallback object is determined by the call to its class constructor. Dostępne są dwie opcje:Two options are available:

W przypadku wybrania ciągu rezerwowego do użycia z tą klasą upewnij się, że ciąg składa się ze znaków, które mogą być zakodowane w kodowaniu docelowym.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. W przeciwnym razie cykliczne wyniki powrotu, powodujące ArgumentException .Otherwise, a recursive fallback results, causing an ArgumentException.

Ta klasa jest jedną z dwóch .NET Framework klas, które implementują różne strategie rezerwowe do obsługi błędów konwersji kodowania.This class is one of two .NET Framework classes that implement different fallback strategies for handling encoding conversion failures. Druga klasa jest EncoderExceptionFallback klasą, która zgłasza, EncoderFallbackException gdy napotkany jest nieprawidłowy znak.The other class is the EncoderExceptionFallback class, which throws an EncoderFallbackException when an invalid character is encountered.

Konstruktory

EncoderReplacementFallback()

Inicjuje nowe wystąpienie klasy EncoderReplacementFallback.Initializes a new instance of the EncoderReplacementFallback class.

EncoderReplacementFallback(String)

Inicjuje nowe wystąpienie EncoderReplacementFallback klasy przy użyciu określonego ciągu zastępczego.Initializes a new instance of the EncoderReplacementFallback class using a specified replacement string.

Właściwości

DefaultString

Pobiera ciąg zastępczy, który jest wartością EncoderReplacementFallback obiektu.Gets the replacement string that is the value of the EncoderReplacementFallback object.

MaxCharCount

Pobiera liczbę znaków w ciągu zamiennym dla EncoderReplacementFallback obiektu.Gets the number of characters in the replacement string for the EncoderReplacementFallback object.

Metody

CreateFallbackBuffer()

Tworzy EncoderFallbackBuffer obiekt, który jest inicjowany przy użyciu ciągu zastępujący tego EncoderReplacementFallback obiektu.Creates a EncoderFallbackBuffer object that is initialized with the replacement string of this EncoderReplacementFallback object.

Equals(Object)

Wskazuje, czy wartość określonego obiektu jest równa EncoderReplacementFallback obiektowi.Indicates whether the value of a specified object is equal to the EncoderReplacementFallback object.

GetHashCode()

Pobiera kod skrótu dla wartości EncoderReplacementFallback obiektu.Retrieves the hash code for the value of the EncoderReplacementFallback object.

GetType()

Pobiera Type bieżące wystąpienie.Gets the Type of the current instance.

(Odziedziczone po Object)
MemberwiseClone()

Tworzy skróconą kopię bieżącego elementu Object .Creates a shallow copy of the current Object.

(Odziedziczone po Object)
ToString()

Zwraca ciąg reprezentujący bieżący obiekt.Returns a string that represents the current object.

(Odziedziczone po Object)

Dotyczy

Zobacz też