Encoder 类
将一组字符转换为一个字节序列。
**命名空间:**System.Text
**程序集:**mscorlib（在 mscorlib.dll 中）
语法
声明
<SerializableAttribute> _
<ComVisibleAttribute(True)> _
Public MustInherit Class Encoder
用法
Dim instance As Encoder
[SerializableAttribute]
[ComVisibleAttribute(true)]
public abstract class Encoder
[SerializableAttribute]
[ComVisibleAttribute(true)]
public ref class Encoder abstract
/** @attribute SerializableAttribute() */
/** @attribute ComVisibleAttribute(true) */
public abstract class Encoder
SerializableAttribute
ComVisibleAttribute(true)
public abstract class Encoder
备注
编码是将一组字符转换为一个字节序列的过程。解码是一个反向操作过程，即将一个编码字节序列转换为一组字符。
Encoder 维护对 GetBytes 的连续调用间的状态信息，因此它可以正确地对跨块的字符序列进行编码。Encoder 还保留数据块结尾的尾部字符并将这些尾部字符用在下一次编码操作中。例如，一个数据块的末尾可能是一个不匹配的高代理项，而与其匹配的低代理项则可能位于下一个数据块中。因此，Decoder 和 Encoder 对网络传输和文件操作很有用，这是因为这些操作通常处理数据块而不是完整的数据流。
GetByteCount 方法确定将有多少字节导致对 Unicode 字符集进行编码，而 GetBytes 方法将执行实际的编码操作。
若要获得此类某个实现的实例，请使用 Encoding 实现的 GetEncoder 方法。
版本注意事项
可以在执行转换操作的过程中对 Decoder 或 Encoder 对象进行序列化。如果在同一版本的 .NET Framework 中对该对象进行反序列化，则其状态保留；如果在另一个版本的 .NET Framework 中对该对象进行反列化，则其状态丢失。
给继承者的说明 从此类继承时，您必须重写所有成员。
示例
下面的代码示例演示如何使用指定的编码将 Unicode 字符数组转换为字节块。为进行比较，首先使用 UTF7Encoding 对字符数组进行编码。然后，再使用 Encoder 对该字符数组进行编码。
Imports System
Imports System.Text
Imports Microsoft.VisualBasic
Imports Microsoft.VisualBasic.Strings
Class EncoderTest
Public Shared Sub Main()
' Unicode characters.
' ChrW(35) = #
' ChrW(37) = %
' ChrW(928) = Pi
' ChrW(931) = Sigma
Dim chars() As Char = {ChrW(35), ChrW(37), ChrW(928), ChrW(931)}
' Encode characters using an Encoding object.
Dim encoding As Encoding = Encoding.UTF7
Console.WriteLine( _
"Using Encoding" & _
ControlChars.NewLine & _
"--------------" _
)
' Encode complete array for comparison.
Dim allCharactersFromEncoding As Byte() = encoding.GetBytes(chars)
Console.WriteLine("All characters encoded:")
ShowArray(allCharactersFromEncoding)
' Encode characters, one-by-one.
' The Encoding object will NOT maintain state between calls.
Dim firstchar As Byte() = encoding.GetBytes(chars, 0, 1)
Console.WriteLine("First character:")
ShowArray(firstchar)
Dim secondchar As Byte() = encoding.GetBytes(chars, 1, 1)
Console.WriteLine("Second character:")
ShowArray(secondchar)
Dim thirdchar As Byte() = encoding.GetBytes(chars, 2, 1)
Console.WriteLine("Third character:")
ShowArray(thirdchar)
Dim fourthchar As Byte() = encoding.GetBytes(chars, 3, 1)
Console.WriteLine("Fourth character:")
ShowArray(fourthchar)
' Now, encode characters using an Encoder object.
Dim encoder As Encoder = encoding.GetEncoder()
Console.WriteLine( _
"Using Encoder" & _
ControlChars.NewLine & _
"-------------" _
)
' Encode complete array for comparison.
Dim allCharactersFromEncoder( _
encoder.GetByteCount(chars, 0, chars.Length, True) _
) As Byte
encoder.GetBytes(chars, 0, chars.Length, allCharactersFromEncoder, 0, True)
Console.WriteLine("All characters encoded:")
ShowArray(allCharactersFromEncoder)
' Do not flush state; i.e. maintain state between calls.
Dim bFlushState As Boolean = False
' Encode characters one-by-one.
' By maintaining state, the Encoder will not store extra bytes in the output.
Dim firstcharNoFlush( _
encoder.GetByteCount(chars, 0, 1, bFlushState) _
) As Byte
encoder.GetBytes(chars, 0, 1, firstcharNoFlush, 0, bFlushState)
Console.WriteLine("First character:")
ShowArray(firstcharNoFlush)
Dim secondcharNoFlush( _
encoder.GetByteCount(chars, 1, 1, bFlushState) _
) As Byte
encoder.GetBytes(chars, 1, 1, secondcharNoFlush, 0, bFlushState)
Console.WriteLine("Second character:")
ShowArray(secondcharNoFlush)
Dim thirdcharNoFlush( _
encoder.GetByteCount(chars, 2, 1, bFlushState) _
) As Byte
encoder.GetBytes(chars, 2, 1, thirdcharNoFlush, 0, bFlushState)
Console.WriteLine("Third character:")
ShowArray(thirdcharNoFlush)
' Must flush state on last call to GetBytes().
bFlushState = True
Dim fourthcharNoFlush( _
encoder.GetByteCount(chars, 3, 1, bFlushState) _
) As Byte
encoder.GetBytes(chars, 3, 1, fourthcharNoFlush, 0, bFlushState)
Console.WriteLine("Fourth character:")
ShowArray(fourthcharNoFlush)
End Sub 'Main
Public Shared Sub ShowArray(theArray As Array)
Dim o As Object
For Each o In theArray
Console.Write("[{0}]", o)
Next o
Console.WriteLine(ControlChars.NewLine)
End Sub 'ShowArray
End Class 'EncoderTest
using System;
using System.Text;
class EncoderTest {
public static void Main() {
// The characters to encode.
Char[] chars = new Char[] {
'\u0023', // #
'\u0025', // %
'\u03a0', // Pi
'\u03a3' // Sigma
};
// Encode characters using an Encoding object.
Encoding encoding = Encoding.UTF7;
Console.WriteLine("Using Encoding\n--------------");
// Encode complete array for comparison.
Byte[] allCharactersFromEncoding = encoding.GetBytes(chars);
Console.WriteLine("All characters encoded:");
ShowArray(allCharactersFromEncoding);
// Encode characters, one-by-one.
// The Encoding object will NOT maintain state between calls.
Byte[] firstchar = encoding.GetBytes(chars, 0, 1);
Console.WriteLine("First character:");
ShowArray(firstchar);
Byte[] secondchar = encoding.GetBytes(chars, 1, 1);
Console.WriteLine("Second character:");
ShowArray(secondchar);
Byte[] thirdchar = encoding.GetBytes(chars, 2, 1);
Console.WriteLine("Third character:");
ShowArray(thirdchar);
Byte[] fourthchar = encoding.GetBytes(chars, 3, 1);
Console.WriteLine("Fourth character:");
ShowArray(fourthchar);
// Now, encode characters using an Encoder object.
Encoder encoder = encoding.GetEncoder();
Console.WriteLine("Using Encoder\n-------------");
// Encode complete array for comparison.
Byte[] allCharactersFromEncoder = new Byte[encoder.GetByteCount(chars, 0, chars.Length, true)];
encoder.GetBytes(chars, 0, chars.Length, allCharactersFromEncoder, 0, true);
Console.WriteLine("All characters encoded:");
ShowArray(allCharactersFromEncoder);
// Do not flush state; i.e. maintain state between calls.
bool bFlushState = false;
// Encode characters one-by-one.
// By maintaining state, the Encoder will not store extra bytes in the output.
Byte[] firstcharNoFlush = new Byte[encoder.GetByteCount(chars, 0, 1, bFlushState)];
encoder.GetBytes(chars, 0, 1, firstcharNoFlush, 0, bFlushState);
Console.WriteLine("First character:");
ShowArray(firstcharNoFlush);
Byte[] secondcharNoFlush = new Byte[encoder.GetByteCount(chars, 1, 1, bFlushState)];
encoder.GetBytes(chars, 1, 1, secondcharNoFlush, 0, bFlushState);
Console.WriteLine("Second character:");
ShowArray(secondcharNoFlush);
Byte[] thirdcharNoFlush = new Byte[encoder.GetByteCount(chars, 2, 1, bFlushState)];
encoder.GetBytes(chars, 2, 1, thirdcharNoFlush, 0, bFlushState);
Console.WriteLine("Third character:");
ShowArray(thirdcharNoFlush);
// Must flush state on last call to GetBytes().
bFlushState = true;
Byte[] fourthcharNoFlush = new Byte[encoder.GetByteCount(chars, 3, 1, bFlushState)];
encoder.GetBytes(chars, 3, 1, fourthcharNoFlush, 0, bFlushState);
Console.WriteLine("Fourth character:");
ShowArray(fourthcharNoFlush);
}
public static void ShowArray(Array theArray) {
foreach (Object o in theArray) {
Console.Write("[{0}]", o);
}
Console.WriteLine("\n");
}
}
using namespace System;
using namespace System::Text;
using namespace System::Collections;
void ShowArray( Array^ theArray )
{
IEnumerator^ myEnum = theArray->GetEnumerator();
while ( myEnum->MoveNext() )
{
Object^ o = safe_cast<Object^>(myEnum->Current);
Console::Write( "[{0}]", o );
}
Console::WriteLine( "\n" );
}
int main()
{
// The characters to encode.
// Pi
// Sigma
array<Char>^chars = {L'\u03a0',L'\u03a3',L'\u03a6',L'\u03a9'};
// Encode characters using an Encoding Object*.
Encoding^ encoding = Encoding::UTF7;
Console::WriteLine( "Using Encoding\n--------------" );
// Encode complete array for comparison.
array<Byte>^allCharactersFromEncoding = encoding->GetBytes( chars );
Console::WriteLine( "All characters encoded:" );
ShowArray( allCharactersFromEncoding );
// Encode characters, one-by-one.
// The Encoding Object* will NOT maintain state between calls.
array<Byte>^firstchar = encoding->GetBytes( chars, 0, 1 );
Console::WriteLine( "First character:" );
ShowArray( firstchar );
array<Byte>^secondchar = encoding->GetBytes( chars, 1, 1 );
Console::WriteLine( "Second character:" );
ShowArray( secondchar );
array<Byte>^thirdchar = encoding->GetBytes( chars, 2, 1 );
Console::WriteLine( "Third character:" );
ShowArray( thirdchar );
array<Byte>^fourthchar = encoding->GetBytes( chars, 3, 1 );
Console::WriteLine( "Fourth character:" );
ShowArray( fourthchar );
// Now, encode characters using an Encoder Object*.
Encoder^ encoder = encoding->GetEncoder();
Console::WriteLine( "Using Encoder\n-------------" );
// Encode complete array for comparison.
array<Byte>^allCharactersFromEncoder = gcnew array<Byte>(encoder->GetByteCount( chars, 0, chars->Length, true ));
encoder->GetBytes( chars, 0, chars->Length, allCharactersFromEncoder, 0, true );
Console::WriteLine( "All characters encoded:" );
ShowArray( allCharactersFromEncoder );
// Do not flush state; i.e. maintain state between calls.
bool bFlushState = false;
// Encode characters one-by-one.
// By maintaining state, the Encoder will not store extra bytes in the output.
array<Byte>^firstcharNoFlush = gcnew array<Byte>(encoder->GetByteCount( chars, 0, 1, bFlushState ));
encoder->GetBytes( chars, 0, 1, firstcharNoFlush, 0, bFlushState );
Console::WriteLine( "First character:" );
ShowArray( firstcharNoFlush );
array<Byte>^secondcharNoFlush = gcnew array<Byte>(encoder->GetByteCount( chars, 1, 1, bFlushState ));
encoder->GetBytes( chars, 1, 1, secondcharNoFlush, 0, bFlushState );
Console::WriteLine( "Second character:" );
ShowArray( secondcharNoFlush );
array<Byte>^thirdcharNoFlush = gcnew array<Byte>(encoder->GetByteCount( chars, 2, 1, bFlushState ));
encoder->GetBytes( chars, 2, 1, thirdcharNoFlush, 0, bFlushState );
Console::WriteLine( "Third character:" );
ShowArray( thirdcharNoFlush );
// Must flush state on last call to GetBytes().
bFlushState = true;
array<Byte>^fourthcharNoFlush = gcnew array<Byte>(encoder->GetByteCount( chars, 3, 1, bFlushState ));
encoder->GetBytes( chars, 3, 1, fourthcharNoFlush, 0, bFlushState );
Console::WriteLine( "Fourth character:" );
ShowArray( fourthcharNoFlush );
}
import System.*;
import System.Text.*;
class EncoderTest
{
public static void main(String[] args)
{
// The characters to encode.
char chars[] = new char[] {
'\u0023', // #
'\u0025', // %
'\u03a0', // Pi
'\u03a3' // Sigma
};
// Encode characters using an Encoding object.
Encoding encoding = Encoding.get_UTF7();
Console.WriteLine("Using Encoding\n--------------");
// Encode complete array for comparison.
ubyte allCharactersFromEncoding[] = encoding.GetBytes(chars);
Console.WriteLine("All characters encoded:");
ShowArray(allCharactersFromEncoding);
// Encode characters, one-by-one.
// The Encoding object will NOT maintain state between calls.
ubyte firstchar[] = encoding.GetBytes(chars, 0, 1);
Console.WriteLine("First character:");
ShowArray(firstchar);
ubyte secondchar[] = encoding.GetBytes(chars, 1, 1);
Console.WriteLine("Second character:");
ShowArray(secondchar);
ubyte thirdchar[] = encoding.GetBytes(chars, 2, 1);
Console.WriteLine("Third character:");
ShowArray(thirdchar);
ubyte fourthchar[] = encoding.GetBytes(chars, 3, 1);
Console.WriteLine("Fourth character:");
ShowArray(fourthchar);
// Now, encode characters using an Encoder object.
Encoder encoder = encoding.GetEncoder();
Console.WriteLine("Using Encoder\n-------------");
// Encode complete array for comparison.
ubyte allCharactersFromEncoder[] = new
ubyte[encoder.GetByteCount(chars, 0, chars.length, true)];
encoder.GetBytes(chars, 0, chars.length,
allCharactersFromEncoder, 0, true);
Console.WriteLine("All characters encoded:");
ShowArray(allCharactersFromEncoder);
// Do not flush state; i.e. maintain state between calls.
boolean bFlushState = false;
// Encode characters one-by-one.
// By maintaining state, the Encoder will not store
// extra bytes in the output.
ubyte firstcharNoFlush[] = new
ubyte[encoder.GetByteCount(chars, 0, 1, bFlushState)];
encoder.GetBytes(chars, 0, 1, firstcharNoFlush, 0, bFlushState);
Console.WriteLine("First character:");
ShowArray(firstcharNoFlush);
ubyte secondcharNoFlush[] = new
ubyte[encoder.GetByteCount(chars, 1, 1, bFlushState)];
encoder.GetBytes(chars, 1, 1, secondcharNoFlush, 0, bFlushState);
Console.WriteLine("Second character:");
ShowArray(secondcharNoFlush);
ubyte thirdcharNoFlush[] = new
ubyte[encoder.GetByteCount(chars, 2, 1, bFlushState)];
encoder.GetBytes(chars, 2, 1, thirdcharNoFlush, 0, bFlushState);
Console.WriteLine("Third character:");
ShowArray(thirdcharNoFlush);
// Must flush state on last call to GetBytes().
bFlushState = true;
ubyte fourthcharNoFlush[] = new
ubyte[encoder.GetByteCount(chars, 3, 1, bFlushState)];
encoder.GetBytes(chars, 3, 1, fourthcharNoFlush, 0, bFlushState);
Console.WriteLine("Fourth character:");
ShowArray(fourthcharNoFlush);
} //main
public static void ShowArray(Array theArray)
{
Object o = null;
for(int iCtr = 0; iCtr < theArray.get_Length(); iCtr++) {
o = theArray.get_Item(iCtr);
Console.Write("[{0}]", o);
}
Console.WriteLine("\n");
} //ShowArray
} //EncoderTest
继承层次结构
System.Object
System.Text.Encoder
线程安全
此类型的任何公共静态（Visual Basic 中的 Shared）成员都是线程安全的，但不保证所有实例成员都是线程安全的。
平台
Windows 98、Windows 2000 SP4、Windows CE、Windows Millennium Edition、Windows Mobile for Pocket PC、Windows Mobile for Smartphone、Windows Server 2003、Windows XP Media Center Edition、Windows XP Professional x64 Edition、Windows XP SP2、Windows XP Starter Edition
.NET Framework 并不是对每个平台的所有版本都提供支持。有关受支持版本的列表，请参见系统要求。
版本信息
.NET Framework
受以下版本支持：2.0、1.1、1.0
.NET Compact Framework
受以下版本支持：2.0、1.0