EncoderExceptionFallback Clase

Definición

Proporciona un mecanismo de control de errores, denominado reserva, aplicable a un carácter de entrada que no se puede convertir en una secuencia de bytes de salida.Provides a failure-handling mechanism, called a fallback, for an input character that cannot be converted to an output byte sequence. La reserva produce una excepción si un carácter de entrada no se puede convertir en una secuencia de bytes de salida.The fallback throws an exception if an input character cannot be converted to an output byte sequence. Esta clase no puede heredarse.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
Herencia
EncoderExceptionFallback
Atributos

Ejemplos

En el ejemplo de código siguiente EncoderExceptionFallback se EncoderFallbackException muestran las clases y.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.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
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...
'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. ***
'

Comentarios

Una codificación asigna un carácter Unicode a una secuencia de bytes codificada, que se puede transferir posteriormente a un medio físico, como un disco o a través de un vínculo de comunicaciones.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. Los caracteres se pueden asignar de varias maneras y una codificación determinada se representa mediante un tipo derivado de la Encoding clase.Characters can be mapped in various ways, and a particular encoding is represented by a type derived from the Encoding class. En concreto, el método del tipo GetBytes de codificación codifica un carácter en una secuencia de bytes y el GetChars método descodifica una secuencia de bytes en un carácter.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.

Se puede producir un error en una operación de codificación si la codificación no puede representar el carácter de entrada.An encoding operation can fail if the input character cannot be represented by the encoding. Por ejemplo, un ASCIIEncoding objeto no puede codificar un carácter que produzca un valor de punto de código Unicode que esté fuera del intervalo de u + 0000 a u + 007F.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.

En los casos en los que no se puede realizar una conversión de codificación o descodificación, el .NET Framework proporciona un mecanismo de control de errores denominado reserva.In cases where an encoding or decoding conversion cannot be performed, the .NET Framework provides a failure-handling mechanism called a fallback. La aplicación puede utilizar la reserva de codificador .NET Framework predefinida, o bien puede crear una reserva de codificador personalizada derivada de las EncoderFallback clases EncoderFallbackBuffer y.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.

El .NET Framework proporciona dos clases predefinidas que implementan diferentes estrategias de reserva para controlar los errores de conversión de codificación.The .NET Framework provides two predefined classes that implement different fallback strategies for handling encoding conversion failures. La EncoderReplacementFallback clase sustituye una cadena proporcionada por cualquier carácter de entrada que no se pueda convertir.The EncoderReplacementFallback class substitutes a string provided for any input character that cannot be converted. La cadena de sustitución se codifica en lugar del carácter no válido y, a continuación, la operación de codificación continúa convirtiendo el resto de la entrada.The substitute string is encoded in place of the invalid character, and then the encoding operation continues converting the remainder of the input. En cambio, la EncoderExceptionFallback clase produce una EncoderFallbackException excepción cuando se encuentra un carácter no válido.In contrast, the EncoderExceptionFallback class throws a EncoderFallbackException when an invalid character is encountered.

Constructores

EncoderExceptionFallback()

Inicializa una nueva instancia de la clase EncoderExceptionFallback.Initializes a new instance of the EncoderExceptionFallback class.

Propiedades

MaxCharCount

Obtiene el número máximo de caracteres que esta instancia puede devolver.Gets the maximum number of characters this instance can return.

Métodos

CreateFallbackBuffer()

Devuelve un búfer de reserva del codificador que produce una excepción si no puede convertir una secuencia de caracteres en una secuencia de bytes.Returns an encoder fallback buffer that throws an exception if it cannot convert a character sequence to a byte sequence.

Equals(Object)

Indica si el objeto EncoderExceptionFallback actual y un objeto especificado son iguales.Indicates whether the current EncoderExceptionFallback object and a specified object are equal.

GetHashCode()

Devuelve el código hash de esta instancia.Retrieves the hash code for this instance.

GetType()

Obtiene el Type de la instancia actual.Gets the Type of the current instance.

(Heredado de Object)
MemberwiseClone()

Crea una copia superficial del objeto Object actual.Creates a shallow copy of the current Object.

(Heredado de Object)
ToString()

Devuelve una cadena que representa el objeto actual.Returns a string that represents the current object.

(Heredado de Object)

Se aplica a

Consulte también: