Encoding.ASCII Encoding.ASCII Encoding.ASCII Encoding.ASCII Property

Definition

Ruft eine Codierung für den ASCII-Zeichensatz (7-Bit) ab.Gets an encoding for the ASCII (7-bit) character set.

public:
 static property System::Text::Encoding ^ ASCII { System::Text::Encoding ^ get(); };
public static System.Text.Encoding ASCII { get; }
member this.ASCII : System.Text.Encoding
Public Shared ReadOnly Property ASCII As Encoding

Eigenschaftswert

Eine Codierung für den ASCII-Zeichensatz (7 Bits).An encoding for the ASCII (7-bit) character set.

Beispiele

Im folgenden Beispiel werden die Auswirkungen der ASCII-Codierung auf Zeichen, die sich außerhalb des ASCII-Bereichs befinden, veranschaulicht.The following example demonstrates the effect of the ASCII encoding on characters that are outside the ASCII range.

using namespace System;
using namespace System::Text;
using namespace System::Collections;
int main()
{
   
   // Create an ASCII encoding.
   Encoding^ ascii = Encoding::ASCII;
   
   // A Unicode String* with two characters outside the ASCII code range.
   String^ unicodeString = L"This unicode string contains two characters with codes outside the ASCII code range, Pi (\u03a0) and Sigma (\u03a3).";
   Console::WriteLine( "Original string:" );
   Console::WriteLine( unicodeString );
   
   // Save the positions of the special characters for later reference.
   int indexOfPi = unicodeString->IndexOf( L'\u03a0' );
   int indexOfSigma = unicodeString->IndexOf( L'\u03a3' );
   
   // Encode the String*.
   array<Byte>^encodedBytes = ascii->GetBytes( unicodeString );
   Console::WriteLine();
   Console::WriteLine( "Encoded bytes:" );
   IEnumerator^ myEnum = encodedBytes->GetEnumerator();
   while ( myEnum->MoveNext() )
   {
      Byte b = safe_cast<Byte>(myEnum->Current);
      Console::Write( "[{0}]", b );
   }

   Console::WriteLine();
   
   // Notice that the special characters have been replaced with
   // the value 63, which is the ASCII character code for '?'.
   Console::WriteLine();
   Console::WriteLine( "Value at position of Pi character: {0}", encodedBytes[ indexOfPi ] );
   Console::WriteLine( "Value at position of Sigma character: {0}", encodedBytes[ indexOfSigma ] );
   
   // Decode bytes back to String*.
   // Notice the missing Pi and Sigma characters.
   String^ decodedString = ascii->GetString( encodedBytes );
   Console::WriteLine();
   Console::WriteLine( "Decoded bytes:" );
   Console::WriteLine( decodedString );
}

/*
This code produces the following output.

Original string:
This unicode string contains two characters with codes outside the ASCII code range, Pi (�) and Sigma (�).

Encoded bytes:
[84][104][105][115][32][117][110][105][99][111][100][101][32][115][116][114][105][110][103][32][99][111][110][116][97][105][110][115][32][116][119][111][32][99][104][97][114][97][99][116][101][114][115][32][119][105][116][104][32][99][111][100][101][115][32][111][117][116][115][105][100][101][32][116][104][101][32][65][83][67][73][73][32][99][111][100][101][32][114][97][110][103][101][44][32][80][105][32][40][63][41][32][97][110][100][32][83][105][103][109][97][32][40][63][41][46]

Value at position of Pi character: 63
Value at position of Sigma character: 63

Decoded bytes:
This unicode string contains two characters with codes outside the ASCII code range, Pi (?) and Sigma (?).

*/

using System;
using System.Text;

class EncodingExample 
{
  public static void Main() 
  {
      // Create an ASCII encoding.
      Encoding ascii = Encoding.ASCII;
  
      // A Unicode string with two characters outside the ASCII code range.
      String unicodeString =
          "This unicode string contains two characters " +
          "with codes outside the ASCII code range, " +
          "Pi (\u03a0) and Sigma (\u03a3).";
      Console.WriteLine("Original string:");
      Console.WriteLine(unicodeString);

      // Save the positions of the special characters for later reference.
      int indexOfPi = unicodeString.IndexOf('\u03a0');
      int indexOfSigma = unicodeString.IndexOf('\u03a3');

      // Encode the string.
      Byte[] encodedBytes = ascii.GetBytes(unicodeString);
      Console.WriteLine();
      Console.WriteLine("Encoded bytes:");
      foreach (Byte b in encodedBytes) 
      {
          Console.Write("[{0}]", b);
      }
      Console.WriteLine();
  
      // Notice that the special characters have been replaced with
      // the value 63, which is the ASCII character code for '?'.
      Console.WriteLine();
      Console.WriteLine(
          "Value at position of Pi character: {0}",
          encodedBytes[indexOfPi]
          );
      Console.WriteLine(
          "Value at position of Sigma character: {0}",
          encodedBytes[indexOfSigma]
          );

      // Decode bytes back to a string.
      // Notice missing the Pi and Sigma characters.
      String decodedString = ascii.GetString(encodedBytes);
      Console.WriteLine();
      Console.WriteLine("Decoded bytes:");
      Console.WriteLine(decodedString);
  }
}
/*
This code produces the following output.

Original string:
This unicode string contains two characters with codes outside the ASCII code range, Pi (ã) and Sigma (ä).

Encoded bytes:
[84][104][105][115][32][117][110][105][99][111][100][101][32][115][116][114][105][110][103][32][99][111][110][116][97][105][110][115][32][116][119][111][32][99][104][97][114][97][99][116][101][114][115][32][119][105][116][104][32][99][111][100][101][115][32][111][117][116][115][105][100][101][32][116][104][101][32][65][83][67][73][73][32][99][111][100][101][32][114][97][110][103][101][44][32][80][105][32][40][63][41][32][97][110][100][32][83][105][103][109][97][32][40][63][41][46]

Value at position of Pi character: 63
Value at position of Sigma character: 63

Decoded bytes:
This unicode string contains two characters with codes outside the ASCII code range, Pi (?) and Sigma (?).

*/
Imports System.Text

Class EncodingExample
  Public Shared Sub Main()
      ' Create and ASCII encoding.
      Dim ascii As Encoding = Encoding.ASCII

      ' A Unicode string with two characters outside the ASCII code range.
      Dim unicodeString As String = "This unicode string contains two characters " + "with codes outside the ASCII code range, " + "Pi (" & ChrW(&H03A0) & ") and Sigma (" & ChrW(&H03A3) & ")."
      Console.WriteLine("Original string:")
      Console.WriteLine(unicodeString)

      ' Save the positions of the special characters for later reference.
      Dim indexOfPi As Integer = unicodeString.IndexOf(ChrW(&H03A0))
      Dim indexOfSigma As Integer = unicodeString.IndexOf(ChrW(&H03A3))

      ' Encode the string.
      Dim encodedBytes As Byte() = ascii.GetBytes(unicodeString)
      Console.WriteLine()
      Console.WriteLine("Encoded bytes:")
      For Each b In encodedBytes
          Console.Write("[{0}]", b)
      Next b
      Console.WriteLine()

      ' Notice that the special characters have been replaced with
      ' the value 63, which is the ASCII character code for '?'.
      Console.WriteLine()
      Console.WriteLine("Value at position of Pi character: {0}", encodedBytes(indexOfPi))
      Console.WriteLine("Value at position of Sigma character: {0}", encodedBytes(indexOfSigma))

      ' Decode bytes back to a string.
      ' Notice missing Pi and Sigma characters.
      Dim decodedString As String = ascii.GetString(encodedBytes)
      Console.WriteLine()
      Console.WriteLine("Decoded bytes:")
      Console.WriteLine(decodedString)
  End Sub
End Class
'This code produces the following output.
'Original string:
'This unicode string contains two characters with codes outside 'the ASCII code range, Pi (ã) and Sigma (ä).
'
'Encoded bytes:
'[84][104][105][115][32][117][110][105][99][111][100][101][32]'[115][116][114][105][110][103][32][99][111][110][116][97]'[105][110][115][32][116][119][111][32][99][104][97][114][97]'[99][116][101][114][115][32][119][105][116][104][32][99][111]'[100][101][115][32][111][117][116][115][105][100][101][32]'[116][104][101][32][65][83][67][73][73][32][99][111][100]'[101][32][114][97][110][103][101][44][32][80][105][32][40]'[63][41][32][97][110][100][32][83][105][103][109][97][32][40]'[63][41][46]
'
'Value at position of Pi character: 63
'Value at position of Sigma character: 63
'
'Decoded bytes:
'This unicode string contains two characters with codes outside 'the ASCII code range, Pi (?) and Sigma (?).
'

Hinweise

ASCII-Zeichen sind auf die niedrigsten 128 Unicode-Zeichen (von U + 0000 bis U + 007F) beschränkt.ASCII characters are limited to the lowest 128 Unicode characters, from U+0000 to U+007F.

Wenn Sie die ASCII-Codierung für Ihre App auswählen, sollten Sie Folgendes beachten:When selecting the ASCII encoding for your app, consider the following:

  • Die ASCII-Codierung ist in der Regel für Protokolle geeignet, für die ASCII erforderlich ist.The ASCII encoding is usually appropriate for protocols that require ASCII.

  • Wenn Sie eine 8-Bit-Codierung benötigen (was manchmal fälschlicherweise als "ASCII" bezeichnet wird), wird die UTF-8-Codierung über die ASCII-Codierung empfohlen.If you requires 8-bit encoding (which is sometimes incorrectly referred to as "ASCII"), the UTF-8 encoding is recommended over the ASCII encoding. Für die Zeichen 0-7f sind die Ergebnisse identisch, aber die Verwendung von UTF-8 vermeidet den Datenverlust, indem die Darstellung aller Unicode-Zeichen, die darstellbar sind, zugelassen wird.For the characters 0-7F, the results are identical, but use of UTF-8 avoids data loss by allowing representation of all Unicode characters that are representable. Beachten Sie, dass die ASCII-Codierung eine 8-Bit-Mehrdeutigkeit aufweist, die böswillige Verwendungsmöglichkeiten zulässt, aber die UTF-8-Codierung entfernt Mehrdeutigkeiten über das 8. Bit.Note that the ASCII encoding has an 8th bit ambiguity that can allow malicious use, but the UTF-8 encoding removes ambiguity about the 8th bit.

  • Vor der .NET Framework Version 2,0 ermöglichte das .NET Framework Spoofing, indem das 8. Bit ignoriert wurde.Prior to the .NET Framework version 2.0, the .NET Framework allowed spoofing by ignoring the 8th bit. Beginnend mit dem .NET Framework 2,0 werden nicht-ASCII-Code Punkte während der Decodierung zurückgegriffen.Beginning with the .NET Framework 2.0, non-ASCII code points fall back during decoding.

Das ASCIIEncoding Objekt, das von dieser Eigenschaft zurückgegeben wird, verfügt möglicherweise nicht über das entsprechende Verhalten für Ihre APP.The ASCIIEncoding object that is returned by this property might not have the appropriate behavior for your app. Er verwendet einen Ersatz Fall Back, um jede Zeichenfolge zu ersetzen, die nicht codiert werden kann, und jedes Byte, das nicht mit einem Fragezeichen ("?") decodiert werden kann.It uses replacement fallback to replace each string that it cannot encode and each byte that it cannot decode with a question mark ("?") character. Stattdessen GetEncoding(String, EncoderFallback, DecoderFallback) können Sie die-Methode zum Instanziieren eines ASCIIEncoding Objekts verwenden, dessen Fall Back entweder ein EncoderFallbackException oder ein DecoderFallbackExceptionist, wie im folgenden Beispiel veranschaulicht.Instead, you can call the GetEncoding(String, EncoderFallback, DecoderFallback) method to instantiate an ASCIIEncoding object whose fallback is either an EncoderFallbackException or a DecoderFallbackException, as the following example illustrates.

using System;
using System.Text;

public class Example
{
   public static void Main()
   {
      Encoding enc = Encoding.GetEncoding("us-ascii", 
                                          new EncoderExceptionFallback(),
                                          new DecoderExceptionFallback());
      string value = "\u00C4 \u00F6 \u00AE"; 
      
      try {
         byte[] bytes= enc.GetBytes(value);
         foreach (var byt in bytes)
            Console.Write("{0:X2} ", byt);
         Console.WriteLine();

         string value2 = enc.GetString(bytes);
         Console.WriteLine(value2);
      }
      catch (EncoderFallbackException e) {
         Console.WriteLine("Unable to encode {0} at index {1}", 
                           e.IsUnknownSurrogate() ? 
                              String.Format("U+{0:X4} U+{1:X4}", 
                                            Convert.ToUInt16(e.CharUnknownHigh),
                                            Convert.ToUInt16(e.CharUnknownLow)) :
                              String.Format("U+{0:X4}", 
                                            Convert.ToUInt16(e.CharUnknown)),
                           e.Index);
      }
   }
}
// The example displays the following output:
//        Unable to encode U+00C4 at index 0
Imports System.Text

Module Example
   Public Sub Main()
      Dim enc As Encoding = Encoding.GetEncoding("us-ascii", 
                                                 New EncoderExceptionFallback(),
                                                 New DecoderExceptionFallback())
      Dim value As String = String.Format("{0} {1} {2}", 
                            ChrW(&h00C4), ChrW(&h00F6), ChrW(&h00AE))
      
      Try
         Dim bytes() As Byte = enc.GetBytes(value)
         For Each byt As Byte In bytes
            Console.Write("{0:X2} ", byt)
         Next       
         Console.WriteLine()
         Dim value2 As String = enc.GetString(bytes)
         Console.WriteLine(value2)
      Catch e As EncoderFallbackException
         Console.WriteLine("Unable to encode {0} at index {1}", 
                           If(e.IsUnknownSurrogate(), 
                              String.Format("U+{0:X4} U+{1:X4}", 
                                            Convert.ToUInt16(e.CharUnknownHigh),
                                            Convert.ToUInt16(e.CharUnknownLow)),
                              String.Format("U+{0:X4}", 
                                            Convert.ToUInt16(e.CharUnknown))),
                           e.Index)
      End Try
   End Sub
End Module
' The example displays the following output:
'       Unable to encode U+00C4 at index 0

Gilt für:

Siehe auch