Encoding.UTF8 Encoding.UTF8 Encoding.UTF8 Encoding.UTF8 Property

Definizione

Ottiene una codifica per il formato UTF-8.Gets an encoding for the UTF-8 format.

public:
 static property System::Text::Encoding ^ UTF8 { System::Text::Encoding ^ get(); };
public static System.Text.Encoding UTF8 { get; }
member this.UTF8 : System.Text.Encoding
Public Shared ReadOnly Property UTF8 As Encoding

Valore della proprietà

Codifica per il formato UTF-8.An encoding for the UTF-8 format.

Esempi

Nell'esempio seguente viene definita una matrice costituita dai caratteri seguenti:The following example defines an array that consists of the following characters:

  • ALFABETO LATINO MINUSCOLO Z (U + 007A)LATIN SMALL LETTER Z (U+007A)

  • LETTERA LATINA MINUSCOLA A (U + 0061)LATIN SMALL LETTER A (U+0061)

  • COMBINAZIONE DI BREVE (U + 0306)COMBINING BREVE (U+0306)

  • PICCOLA LETTERA LATINA AE CON ACUTA (U + 01FD)LATIN SMALL LETTER AE WITH ACUTE (U+01FD)

  • GRECO PICCOLA LETTERA BETA (U + 03B2)GREEK SMALL LETTER BETA (U+03B2)

  • Una coppia di surrogati (U + D800 U + DD54) che Forms GREEK ACROFONICO ATTIC 1000 STATEers (U + 10154).A surrogate pair (U+D800 U+DD54) that forms GREEK ACROPHONIC ATTIC ONE THOUSAND STATERS (U+10154).

Vengono visualizzate le unità di codice UTF-16 di ogni carattere e viene determinato il numero di byte richiesti da un codificatore UTF-8 per codificare la matrice di caratteri.It displays the UTF-16 code units of each character and determines the number of bytes required by a UTF-8 encoder to encode the character array. Codifica quindi i caratteri e Visualizza i byte con codifica UTF-8 risultanti.It then encodes the characters and displays the resulting UTF-8-encoded bytes.

using System;
using System.Text;

public class Example
{
   public static void Main()  
   {
      // Create a character array.
      string gkNumber = Char.ConvertFromUtf32(0x10154);
      char[] chars = new char[] { 'z', 'a', '\u0306', '\u01FD', '\u03B2', 
                                  gkNumber[0], gkNumber[1] };

      // Get UTF-8 and UTF-16 encoders.
      Encoding utf8 = Encoding.UTF8;
      Encoding utf16 = Encoding.Unicode;
      
      // Display the original characters' code units.
      Console.WriteLine("Original UTF-16 code units:");
      byte[] utf16Bytes = utf16.GetBytes(chars);
      foreach (var utf16Byte in utf16Bytes)
         Console.Write("{0:X2} ", utf16Byte);
      Console.WriteLine();
         
      // Display the number of bytes required to encode the array.
      int reqBytes  = utf8.GetByteCount(chars);
      Console.WriteLine("\nExact number of bytes required: {0}", 
                    reqBytes);

      // Display the maximum byte count.
      int maxBytes = utf8.GetMaxByteCount(chars.Length);
      Console.WriteLine("Maximum number of bytes required: {0}\n", 
                        maxBytes);

      // Encode the array of chars.
      byte[] utf8Bytes = utf8.GetBytes(chars);

      // Display all the UTF-8-encoded bytes.
      Console.WriteLine("UTF-8-encoded code units:");
      foreach (var utf8Byte in utf8Bytes)
         Console.Write("{0:X2} ", utf8Byte);
      Console.WriteLine();
   }
}
// The example displays the following output:
//       Original UTF-16 code units:
//       7A 00 61 00 06 03 FD 01 B2 03 00 D8 54 DD
//       
//       Exact number of bytes required: 12
//       Maximum number of bytes required: 24
//       
//       UTF-8-encoded code units:
//       7A 61 CC 86 C7 BD CE B2 F0 90 85 94
Imports System.Text

Public Module Example
   Public Sub Main()
      ' Create a character array.
      Dim gkNumber As String = Char.ConvertFromUtf32(&h10154)
      Dim chars() As Char = {"z"c, "a"c, ChrW(&H0306), ChrW(&H01FD), 
                             ChrW(&H03B2), gkNumber(0), gkNumber(1) }
 
      ' Get UTF-8 and UTF-16 encoders.
      Dim utf8 As Encoding = Encoding.UTF8
      Dim utf16 As Encoding = Encoding.Unicode

      ' Display the original characters' code units.
      Console.WriteLine("Original UTF-16 code units:")
      Dim utf16Bytes() As Byte = utf16.GetBytes(chars)
      For Each utf16Byte In utf16Bytes
         Console.Write("{0:X2} ", utf16Byte)
      Next
      Console.WriteLine()

      Console.WriteLine()
      ' Display the number of bytes required to encode the array.
      Dim reqBytes As Integer = utf8.GetByteCount(chars)
      Console.WriteLine("Exact number of bytes required: {0}", 
                        reqBytes)

      ' Display the maximum byte count.
      Dim maxBytes As Integer = utf8.GetMaxByteCount(chars.Length)
      Console.WriteLine("Maximum number of bytes required: {0}", 
                        maxBytes)
      Console.WriteLine()
      
      ' Encode the array of characters.
      Dim utf8Bytes() As Byte = utf8.GetBytes(chars)

      ' Display all the UTF-8-encoded bytes.
      Console.WriteLine("UTF-8-encoded code units:")
      For Each utf8Byte In utf8Bytes
         Console.Write("{0:X2} ", utf8Byte)
      Next
      Console.WriteLine()
   End Sub 
End Module 
' The example displays the following output:
'    Original UTF-16 code units:
'    7A 00 61 00 06 03 FD 01 B2 03 00 D8 54 DD
'    
'    Exact number of bytes required: 12
'    Maximum number of bytes required: 24
'    
'    UTF-8-encoded code units:
'    7A 61 CC 86 C7 BD CE B2 F0 90 85 94

Commenti

Questa proprietà restituisce un UTF8Encoding oggetto che codifica i caratteri Unicode (con codifica UTF-16) in una sequenza da uno a quattro byte per carattere e che decodifica una matrice di byte codificata in UTF-8 in caratteri Unicode (UTF-16).This property returns a UTF8Encoding object that encodes Unicode (UTF-16-encoded) characters into a sequence of one to four bytes per character, and that decodes a UTF-8-encoded byte array to Unicode (UTF-16-encoded) characters. Per informazioni sulle codifiche di caratteri supportate da .NET e su una descrizione della codifica Unicode da usare, vedere codifica dei caratteri in .NET.For information about the character encodings supported by .NET and a discussion of which Unicode encoding to use, see Character Encoding in .NET.

L' UTF8Encoding oggetto restituito da questa proprietà potrebbe non avere il comportamento appropriato per l'app.The UTF8Encoding object that is returned by this property might not have the appropriate behavior for your app.

  • Restituisce un UTF8Encoding oggetto che fornisce un byte order mark Unicode (BOM).It returns a UTF8Encoding object that provides a Unicode byte order mark (BOM). Per creare un'istanza di una codifica UTF8 che non fornisce un BOM, chiamare un overload UTF8Encoding del costruttore.To instantiate a UTF8 encoding that doesn't provide a BOM, call any overload of the UTF8Encoding constructor.

  • Restituisce un UTF8Encoding oggetto che usa il fallback di sostituzione per sostituire ogni stringa che non può codificare e ogni byte che non può decodificare con un punto interrogativo ("?").It returns a UTF8Encoding object that uses replacement fallback to replace each string that it can't encode and each byte that it can't decode with a question mark ("?") character. È invece possibile chiamare il costruttore UTF8Encoding.UTF8Encoding(Boolean, Boolean) per creare un'istanza di UTF8Encoding un oggetto il EncoderFallbackException cui fallback DecoderFallbackExceptionè o, come illustrato nell'esempio riportato di seguito.Instead, you can call the UTF8Encoding.UTF8Encoding(Boolean, Boolean) constructor to instantiate a UTF8Encoding 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 = new UTF8Encoding(true, true);
          string value = "\u00C4 \uD802\u0033 \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+D802 at index 2
    
    Imports System.Text
    
    Module Example
       Public Sub Main()
          Dim enc As Encoding = New UTF8Encoding(True, True)
          Dim value As String = String.Format("{0} {1}{2} {3}", 
                                ChrW(&h00C4), ChrW(&hD802), ChrW(&h0033), 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+D802 at index 2
    

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