EncoderReplacementFallback EncoderReplacementFallback EncoderReplacementFallback EncoderReplacementFallback Class

Definição

Fornece um mecanismo de tratamento de falha chamado fallback para um caractere de entrada que não pode ser convertido em uma sequência de bytes de saída.Provides a failure handling mechanism, called a fallback, for an input character that cannot be converted to an output byte sequence. O fallback usa uma cadeia de caracteres de substituição especificada pelo usuário, em vez do caractere de entrada original.The fallback uses a user-specified replacement string instead of the original input character. Essa classe não pode ser herdada.This class cannot be inherited.

public ref class EncoderReplacementFallback sealed : System::Text::EncoderFallback
[System.Serializable]
public sealed class EncoderReplacementFallback : System.Text.EncoderFallback
type EncoderReplacementFallback = class
    inherit EncoderFallback
Public NotInheritable Class EncoderReplacementFallback
Inherits EncoderFallback
Herança
EncoderReplacementFallbackEncoderReplacementFallbackEncoderReplacementFallbackEncoderReplacementFallback
Atributos

Exemplos

O exemplo a seguir demonstra EncoderReplacementFallback a classe.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;

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

    // 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;

// --------------------------------------------------------------------------
    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);
    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
        
        ' --------------------------------------------------------------------------
        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)
        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 '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...
'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)"
'

Comentários

Um motivo comum para uma operação de codificação ou decodificação a falhar é se a classe de codificação subjacente não fornecer um mapeamento entre um caractere e uma sequência de bytes equivalente.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. Por exemplo, um ASCIIEncoding objeto não pode codificar um caractere com um valor de ponto de código Unicode que está fora do intervalo de u + 0000 a 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. Se o caractere de entrada não puder ser convertido em uma sequência de bytes EncoderReplacementFallback de saída, um objeto substituirá uma cadeia de caracteres de substituição especificada para o caractere de entrada original.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. O processo de conversão codifica a cadeia de caracteres de substituição e continua a processar o restante da entrada original.The conversion process encodes the replacement string and then continues to process the remainder of the original input.

A cadeia de caracteres de substituição EncoderReplacementFallback usada por um objeto é determinada pela chamada para seu construtor de classe.The replacement string used by an EncoderReplacementFallback object is determined by the call to its class constructor. Duas opções estão disponíveis:Two options are available:

Se você escolher uma cadeia de caracteres de fallback para usar com essa classe, verifique se a cadeia de caracteres é composta inteiramente de caracteres que podem ser codificados na codificação de destino.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. Caso contrário, um resultado de fallback recursivo, ArgumentExceptioncausando um.Otherwise, a recursive fallback results, causing an ArgumentException.

Essa classe é uma das duas classes .NET Framework que implementam estratégias de fallback diferentes para lidar com falhas de conversão de codificação.This class is one of two .NET Framework classes that implement different fallback strategies for handling encoding conversion failures. A outra classe é a EncoderExceptionFallback classe, que gera um EncoderFallbackException quando um caractere inválido é encontrado.The other class is the EncoderExceptionFallback class, which throws an EncoderFallbackException when an invalid character is encountered.

Construtores

EncoderReplacementFallback() EncoderReplacementFallback() EncoderReplacementFallback() EncoderReplacementFallback()

Inicializa uma nova instância da classe EncoderReplacementFallback.Initializes a new instance of the EncoderReplacementFallback class.

EncoderReplacementFallback(String) EncoderReplacementFallback(String) EncoderReplacementFallback(String) EncoderReplacementFallback(String)

Inicializa uma nova instância da classe EncoderReplacementFallback usando uma cadeia de caracteres substituta especificada.Initializes a new instance of the EncoderReplacementFallback class using a specified replacement string.

Propriedades

DefaultString DefaultString DefaultString DefaultString

Obtém a cadeia de caracteres substituta que é o valor do objeto EncoderReplacementFallback.Gets the replacement string that is the value of the EncoderReplacementFallback object.

MaxCharCount MaxCharCount MaxCharCount MaxCharCount

Obtém o número de caracteres na cadeia de caracteres substituta para o objeto EncoderReplacementFallback.Gets the number of characters in the replacement string for the EncoderReplacementFallback object.

Métodos

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

Cria um objeto EncoderFallbackBuffer que é inicializado com a cadeia de caracteres substituta desse objeto EncoderReplacementFallback.Creates a EncoderFallbackBuffer object that is initialized with the replacement string of this EncoderReplacementFallback object.

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

Indica se o valor de um objeto especificado é igual ao do objeto EncoderReplacementFallback.Indicates whether the value of a specified object is equal to the EncoderReplacementFallback object.

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

Recupera o código hash para o valor do objeto EncoderReplacementFallback.Retrieves the hash code for the value of the EncoderReplacementFallback object.

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

Obtém o Type da instância atual.Gets the Type of the current instance.

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

Cria uma cópia superficial do Object atual.Creates a shallow copy of the current Object.

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

Retorna uma cadeia de caracteres que representa o objeto atual.Returns a string that represents the current object.

(Inherited from Object)

Aplica-se a

Veja também