Encoding.UTF8 属性

参考

定义

命名空间:: System.Text

程序集:: System.Text.Encoding.dll

程序集:: System.Runtime.dll

程序集:: netstandard.dll

程序集:: mscorlib.dll

重要

一些信息与预发行产品相关，相应产品在发行之前可能会进行重大修改。对于此处提供的信息，Microsoft 不作任何明示或暗示的担保。

获取 UTF-8 格式的编码。

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

属性值

Encoding

UTF-8 格式的编码。

示例

下面的示例定义一个包含以下字符的数组：

拉丁文小写字母 Z （U + 007A）
拉丁文小写字母 A （U + 0061）
组合短音符（U + 0306）
拉丁文小写字母 AE WITH 锐音符（U + 01FD）
希腊文小写字母 BETA （U + 03B2）
构成希腊语 ACROPHONIC 阁楼 1000 STATERS （U + 10154）的代理项对（U + D800 U + DD54）。

它显示每个字符的 UTF-16 代码单元，并确定 UTF-8 编码器对字符数组进行编码所需的字节数。然后，它对字符进行编码，并显示生成的 UTF-8 编码字节。

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

注解

此属性返回一个 UTF8Encoding 对象，该对象将 Unicode （utf-16 编码的）字符编码为每个字符一至四个字节的序列，并将 utf-8 编码的字节数组解码为 Unicode （utf-16 编码的）字符。有关 .NET 支持的字符编码以及要使用的 Unicode 编码的讨论，请参阅.net 中的字符编码。

UTF8Encoding此属性返回的对象可能没有适用于你的应用程序的行为。

它将返回一个 UTF8Encoding 对象，该对象提供一个 Unicode 字节顺序标记（BOM）。若要实例化不提供 BOM 的 UTF8 编码，请调用构造函数的任何重载 UTF8Encoding 。

它将返回一个 UTF8Encoding 对象，该对象使用替换回退来替换每个无法编码的字符串，以及无法使用问号（"？"）字符解码的每个字节。相反，你可以调用 UTF8Encoding.UTF8Encoding(Boolean, Boolean) 构造函数来实例化 UTF8Encoding 其回退为 EncoderFallbackException 或的对象 DecoderFallbackException ，如下例所示。

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

适用于

Encoding.UTF8 属性

定义

属性值

示例

注解

适用于

另请参阅

其他资源