UnicodeEncoding 类

定义

public ref class UnicodeEncoding : System::Text::Encoding

public class UnicodeEncoding : System.Text.Encoding

[System.Serializable]
public class UnicodeEncoding : System.Text.Encoding

[System.Serializable]
[System.Runtime.InteropServices.ComVisible(true)]
public class UnicodeEncoding : System.Text.Encoding

type UnicodeEncoding = class
    inherit Encoding

[<System.Serializable>]
type UnicodeEncoding = class
    inherit Encoding

[<System.Serializable>]
[<System.Runtime.InteropServices.ComVisible(true)>]
type UnicodeEncoding = class
    inherit Encoding

Public Class UnicodeEncoding
Inherits Encoding

继承

Object

Encoding

UnicodeEncoding

属性

SerializableAttribute ComVisibleAttribute

示例

以下示例演示如何使用 UnicodeEncoding 对象将 Unicode 字符的字符串编码为字节数组。 字节数组被解码为字符串，以证明不会丢失数据。

using System;
using System.Text;

class UnicodeEncodingExample {
    public static void Main() {
        // The encoding.
        UnicodeEncoding unicode = new UnicodeEncoding();
        
        // Create a string that contains Unicode characters.
        String unicodeString =
            "This Unicode string contains two characters " +
            "with codes outside the traditional ASCII code range, " +
            "Pi (\u03a0) and Sigma (\u03a3).";
        Console.WriteLine("Original string:");
        Console.WriteLine(unicodeString);

        // Encode the string.
        Byte[] encodedBytes = unicode.GetBytes(unicodeString);
        Console.WriteLine();
        Console.WriteLine("Encoded bytes:");
        foreach (Byte b in encodedBytes) {
            Console.Write("[{0}]", b);
        }
        Console.WriteLine();
        
        // Decode bytes back to string.
        // Notice Pi and Sigma characters are still present.
        String decodedString = unicode.GetString(encodedBytes);
        Console.WriteLine();
        Console.WriteLine("Decoded bytes:");
        Console.WriteLine(decodedString);
    }
}

Imports System.Text
Imports Microsoft.VisualBasic.Strings

Class UnicodeEncodingExample
    
    Public Shared Sub Main()
        ' The encoding.
        Dim uni As New UnicodeEncoding()
        
        ' Create a string that contains Unicode characters.
        Dim unicodeString As String = _
            "This Unicode string contains two characters " & _
            "with codes outside the traditional ASCII code range, " & _
            "Pi (" & ChrW(928) & ") and Sigma (" & ChrW(931) & ")."
        Console.WriteLine("Original string:")
        Console.WriteLine(unicodeString)
        
        ' Encode the string.
        Dim encodedBytes As Byte() = uni.GetBytes(unicodeString)
        Console.WriteLine()
        Console.WriteLine("Encoded bytes:")
        Dim b As Byte
        For Each b In  encodedBytes
            Console.Write("[{0}]", b)
        Next b
        Console.WriteLine()
        
        ' Decode bytes back to string.
        ' Notice Pi and Sigma characters are still present.
        Dim decodedString As String = uni.GetString(encodedBytes)
        Console.WriteLine()
        Console.WriteLine("Decoded bytes:")
        Console.WriteLine(decodedString)
    End Sub
End Class

以下示例使用与上一个字符串相同的字符串，只不过它将编码的字节写入文件，并使用字节顺序标记（BOM）为字节流添加前缀。 然后，它以两种不同的方式读取文件：使用 StreamReader 对象作为文本文件;作为二进制文件。 正如预期的那样，新读取的字符串都不包括 BOM。

using System;
using System.IO;
using System.Text;

public class Example
{
   public static void Main()
   {
        // Create a UTF-16 encoding that supports a BOM.
        Encoding unicode = new UnicodeEncoding();

        // A Unicode string with two characters outside an 8-bit code range.
        String unicodeString =
            "This Unicode string has 2 characters outside the " +
            "ASCII range: \n" +
            "Pi (\u03A0)), and Sigma (\u03A3).";
        Console.WriteLine("Original string:");
        Console.WriteLine(unicodeString);
        Console.WriteLine();

        // Encode the string.
        Byte[] encodedBytes = unicode.GetBytes(unicodeString);
        Console.WriteLine("The encoded string has {0} bytes.\n",
                          encodedBytes.Length);

        // Write the bytes to a file with a BOM.
        var fs = new FileStream(@".\UTF8Encoding.txt", FileMode.Create);
        Byte[] bom = unicode.GetPreamble();
        fs.Write(bom, 0, bom.Length);
        fs.Write(encodedBytes, 0, encodedBytes.Length);
        Console.WriteLine("Wrote {0} bytes to the file.\n", fs.Length);
        fs.Close();

        // Open the file using StreamReader.
        var sr = new StreamReader(@".\UTF8Encoding.txt");
        String newString = sr.ReadToEnd();
        sr.Close();
        Console.WriteLine("String read using StreamReader:");
        Console.WriteLine(newString);
        Console.WriteLine();

        // Open the file as a binary file and decode the bytes back to a string.
        fs = new FileStream(@".\UTF8Encoding.txt", FileMode.Open);
        Byte[] bytes = new Byte[fs.Length];
        fs.Read(bytes, 0, (int)fs.Length);
        fs.Close();

        String decodedString = unicode.GetString(bytes);
        Console.WriteLine("Decoded bytes:");
        Console.WriteLine(decodedString);
   }
}
// The example displays the following output:
//    Original string:
//    This Unicode string has 2 characters outside the ASCII range:
//    Pi (π), and Sigma (Σ).
//
//    The encoded string has 172 bytes.
//
//    Wrote 174 bytes to the file.
//
//    String read using StreamReader:
//    This Unicode string has 2 characters outside the ASCII range:
//    Pi (π), and Sigma (Σ).
//
//    Decoded bytes:
//    This Unicode string has 2 characters outside the ASCII range:
//    Pi (π), and Sigma (Σ).

Imports System.IO
Imports System.Text

Class Example
    Public Shared Sub Main()
        ' Create a UTF-16 encoding that supports a BOM.
        Dim unicode As New UnicodeEncoding()
        
        ' A Unicode string with two characters outside an 8-bit code range.
        Dim unicodeString As String = _
            "This Unicode string has 2 characters outside the " &
            "ASCII range: " & vbCrLf &
            "Pi (" & ChrW(&h03A0) & "), and Sigma (" & ChrW(&h03A3) & ")."
        Console.WriteLine("Original string:")
        Console.WriteLine(unicodeString)
        Console.WriteLine()
        
        ' Encode the string.
        Dim encodedBytes As Byte() = unicode.GetBytes(unicodeString)
        Console.WriteLine("The encoded string has {0} bytes.",
                          encodedBytes.Length)
        Console.WriteLine()
        
        ' Write the bytes to a file with a BOM.
        Dim fs As New FileStream(".\UnicodeEncoding.txt", FileMode.Create)
        Dim bom() As Byte = unicode.GetPreamble()
        fs.Write(bom, 0, bom.Length)
        fs.Write(encodedBytes, 0, encodedBytes.Length)
        Console.WriteLine("Wrote {0} bytes to the file.", fs.Length)
        fs.Close()
        Console.WriteLine()
        
        ' Open the file using StreamReader.
        Dim sr As New StreamReader(".\UnicodeEncoding.txt")
        Dim newString As String = sr.ReadToEnd()
        sr.Close()
        Console.WriteLine("String read using StreamReader:")
        Console.WriteLine(newString)
        Console.WriteLine()
        
        ' Open the file as a binary file and decode the bytes back to a string.
        fs = new FileStream(".\UnicodeEncoding.txt", FileMode.Open)
        Dim bytes(fs.Length - 1) As Byte
        fs.Read(bytes, 0, fs.Length)
        fs.Close()

        Dim decodedString As String = unicode.GetString(bytes)
        Console.WriteLine("Decoded bytes:")
        Console.WriteLine(decodedString)
    End Sub
End Class
' The example displays the following output:
'    Original string:
'    This Unicode string has 2 characters outside the ASCII range:
'    Pi (π), and Sigma (Σ).
'
'    The encoded string has 172 bytes.
'
'    Wrote 174 bytes to the file.
'
'    String read using StreamReader:
'    This Unicode string has 2 characters outside the ASCII range:
'    Pi (π), and Sigma (Σ).
'
'    Decoded bytes:
'    This Unicode string has 2 characters outside the ASCII range:
'    Pi (π), and Sigma (Σ).

注解

编码是将一组 Unicode 字符转换为字节序列的过程。 解码是将编码字节序列转换为一组 Unicode 字符的过程。

Unicode Standard 为每个受支持的脚本中的每个字符分配一个代码点（一个数字）。 Unicode 转换格式（UTF）是编码该代码点的方法。 Unicode 标准版使用以下 UTF：

• UTF-8，将每个代码点表示为一到四个字节的序列。

• UTF-16，将每个代码点表示为一到两个 16 位整数的序列。

• UTF-32，表示每个代码点为 32 位整数。

有关 UTF 和支持的其他编码 System.Text的详细信息，请参阅 .NET Framework 中的字符编码。

该 UnicodeEncoding 类表示 UTF-16 编码。 编码器可以使用大字节字节顺序（最重要字节第一）或小字节字节顺序（第一个最小有效字节）。 例如，拉丁文大写字母 A（代码点 U+0041）按如下方式序列化（十六进制）：

• 大尾字节顺序： 00 00 00 41

• 小尾字节顺序： 41 00 00 00

使用特定平台的本机字节顺序存储 Unicode 字符通常更有效。 例如，最好在小端平台（如 Intel 计算机）上使用小端字节序。 该 UnicodeEncoding 类对应于 Windows 代码页 1200（小字节顺序）和 1201（大字节字节顺序）。 可以通过调用 BitConverter.IsLittleEndian 该方法来确定特定体系结构的“endianness”。

（可选）对象 UnicodeEncoding 提供字节顺序标记（BOM），它是一个字节数组，可以前缀为编码过程生成的字节序列。 如果前言包含字节顺序标记（BOM），则它有助于解码器确定字节顺序和转换格式或 UTF。

UnicodeEncoding如果实例配置为提供 BOM，则可以通过调用GetPreamble该方法来检索它;否则，该方法将返回一个空数组。 请注意，即使为 BOM 支持配置了对象 UnicodeEncoding ，也必须在编码字节流的开头包含 BOM;类的 UnicodeEncoding 编码方法不会自动执行此操作。

可以通过多种方式实例化对象 UnicodeEncoding ，具体取决于是要提供字节顺序标记（BOM），是想要使用 big-endian 还是 little-endian 编码，以及是否要启用错误检测。 下表列出了UnicodeEncoding返回对象的UnicodeEncoding构造函数和Encoding属性。

该方法 GetByteCount 确定对一组 Unicode 字符进行编码的字节数，该方法 GetBytes 执行实际编码。

同样，该方法 GetCharCount 确定对字节序列进行解码的字符数，以及 GetChars 执行 GetString 实际解码的方法。

对于能够保存状态信息的编码器或解码器，当编码或解码跨越多个块的数据（如编码为 100,000 个字符段的字符串）时，请分别使用 GetEncoder 和 GetDecoder 属性。

另请参阅

• Encoding
• Encoder
• Decoder
• UTF32Encoding
• UTF8Encoding
• UTF7Encoding
• ASCIIEncoding
• UnicodeCategory
• CharUnicodeInfo
• 了解编码