EncoderExceptionFallback 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. Rezerwa zgłasza wyjątek, jeśli nie można przekonwertować znaku wejściowego na sekwencję bajtów wyjściowych.The fallback throws an exception if an input character cannot be converted to an output byte sequence. Klasa ta nie może być dziedziczona.This class cannot be inherited.

public ref class EncoderExceptionFallback sealed : System::Text::EncoderFallback
public sealed class EncoderExceptionFallback : System.Text.EncoderFallback
[System.Serializable]
public sealed class EncoderExceptionFallback : System.Text.EncoderFallback
type EncoderExceptionFallback = class
    inherit EncoderFallback
[<System.Serializable>]
type EncoderExceptionFallback = class
    inherit EncoderFallback
Public NotInheritable Class EncoderExceptionFallback
Inherits EncoderFallback
Dziedziczenie
EncoderExceptionFallback
Atrybuty

Przykłady

Poniższy przykład kodu demonstruje EncoderExceptionFallback EncoderFallbackException klasy i.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. ***
'

Uwagi

Kodowanie mapuje znak Unicode na zakodowaną sekwencję bajtów, którą można następnie przenieść do nośnika fizycznego, na przykład dysku lub za pośrednictwem linku komunikacyjnego.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. Znaki mogą być mapowane na różne sposoby, a określone kodowanie jest reprezentowane przez typ pochodzący od Encoding klasy.Characters can be mapped in various ways, and a particular encoding is represented by a type derived from the Encoding class. W oddzielnym zakresie Metoda typu kodowania GetBytes koduje znak na sekwencję bajtów, a GetChars Metoda dekoduje sekwencję bajtów do znaku.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.

Operacja kodowania może zakończyć się niepowodzeniem, jeśli znak wejściowy nie może być reprezentowany przez kodowanie.An encoding operation can fail if the input character cannot be represented by the encoding. Na przykład ASCIIEncoding obiekt nie może kodować znaku, który zwraca wartość punktu kodu Unicode, która znajduje się poza zakresem u + 0000 do 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.

W przypadkach, gdy nie można wykonać konwersji kodowania lub dekodowania, .NET Framework zapewnia mechanizm obsługi niepowodzeń o nazwie Fallback.In cases where an encoding or decoding conversion cannot be performed, the .NET Framework provides a failure-handling mechanism called a fallback. Twoja aplikacja może korzystać ze wstępnie zdefiniowanej rezerwy .NET Framework Encoder lub utworzyć niestandardową rezerwę kodera pochodzącą od EncoderFallback EncoderFallbackBuffer klas i.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 udostępnia dwie wstępnie zdefiniowane klasy, które implementują różne strategie rezerwowe do obsługi błędów konwersji kodowania.The .NET Framework provides two predefined classes that implement different fallback strategies for handling encoding conversion failures. EncoderReplacementFallbackKlasa zastępuje ciąg podany dla dowolnego znaku wejściowego, którego nie można przekonwertować.The EncoderReplacementFallback class substitutes a string provided for any input character that cannot be converted. Podstawiany ciąg jest zakodowany w miejscu nieprawidłowego znaku, a następnie Operacja kodowania kontynuuje konwersję reszty danych wejściowych.The substitute string is encoded in place of the invalid character, and then the encoding operation continues converting the remainder of the input. Z kolei EncoderExceptionFallback Klasa zgłasza, EncoderFallbackException gdy napotkany jest nieprawidłowy znak.In contrast, the EncoderExceptionFallback class throws a EncoderFallbackException when an invalid character is encountered.

Konstruktory

EncoderExceptionFallback()

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

Właściwości

MaxCharCount

Pobiera maksymalną liczbę znaków, jaką może zwrócić to wystąpienie.Gets the maximum number of characters this instance can return.

Metody

CreateFallbackBuffer()

Zwraca bufor rezerwowy kodera, który zgłasza wyjątek, jeśli nie można skonwertować sekwencji znaków na sekwencję bajtów.Returns an encoder fallback buffer that throws an exception if it cannot convert a character sequence to a byte sequence.

Equals(Object)

Wskazuje, czy bieżący EncoderExceptionFallback obiekt i określony obiekt są równe.Indicates whether the current EncoderExceptionFallback object and a specified object are equal.

GetHashCode()

Pobiera kod skrótu dla tego wystąpienia.Retrieves the hash code for this instance.

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