UTF7Encoding 类
表示 Unicode 字符的 UTF-7 编码。
**命名空间:**System.Text
**程序集:**mscorlib（在 mscorlib.dll 中）
语法
声明
<SerializableAttribute> _
<ComVisibleAttribute(True)> _
Public Class UTF7Encoding
Inherits Encoding
用法
Dim instance As UTF7Encoding
[SerializableAttribute]
[ComVisibleAttribute(true)]
public class UTF7Encoding : Encoding
[SerializableAttribute]
[ComVisibleAttribute(true)]
public ref class UTF7Encoding : public Encoding
/** @attribute SerializableAttribute() */
/** @attribute ComVisibleAttribute(true) */
public class UTF7Encoding extends Encoding
SerializableAttribute
ComVisibleAttribute(true)
public class UTF7Encoding extends Encoding
备注
编码是一个将一组 Unicode 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 Unicode 字符。
Unicode 标准为所有支持脚本中的每个字符分配一个码位（一个数字）。Unicode 转换格式 (UTF) 是一种码位编码方式。Unicode 标准 3.2 版使用下列 UTF：
UTF-8，它将每个码位表示为一个由 1 至 4 个字节组成的序列。
UTF-16，它将每个码位表示为一个由 1 至 2 个 16 位整数组成的序列。
UTF-32，它将每个码位表示为一个 32 位整数。
警告
UTF7Encoding 不提供错误检测。出于安全原因，建议您使用 UTF8Encoding、UnicodeEncoding 或 UTF32Encoding 并启用错误检测。
GetByteCount 方法确定将有多少字节对一组 Unicode 字符进行编码，而 GetBytes 方法将执行实际的编码操作。
同样，GetCharCount 方法确定将有多少字符对字节序列进行解码，而 GetChars 和 GetString 方法执行实际的解码。
UTF7Encoding 对应于 Windows 代码页 65000。
提示
如果使用不同的 .NET Framework 版本来序列化和反序列化对象，则不保留以 UTF-7 编码的对象的状态。
示例
下面的代码示例演示了如何使用 UTF7Encoding 对 Unicode 字符串进行编码，并将它们存储在字节数组中。注意，当字节数组被解码为一个字符串时，数据不会丢失。
Imports System
Imports System.Text
Imports Microsoft.VisualBasic.Strings
Class UTF7EncodingExample
Public Shared Sub Main()
' Create a UTF-7 encoding.
Dim utf7 As New UTF7Encoding()
' A Unicode string with two characters outside a 7-bit code range.
Dim unicodeString As String = _
"This Unicode string contains two characters " & _
"with codes outside a 7-bit code range, " & _
"Pi (" & ChrW(928) & ") and Sigma (" & ChrW(931) & ")."
Console.WriteLine("Original string:")
Console.WriteLine(unicodeString)
' Encode the string.
Dim encodedBytes As Byte() = utf7.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 = utf7.GetString(encodedBytes)
Console.WriteLine()
Console.WriteLine("Decoded bytes:")
Console.WriteLine(decodedString)
End Sub
End Class
using System;
using System.Text;
class UTF7EncodingExample {
public static void Main() {
// Create a UTF-7 encoding.
UTF7Encoding utf7 = new UTF7Encoding();
// A Unicode string with two characters outside a 7-bit code range.
String unicodeString =
"This Unicode string contains two characters " +
"with codes outside a 7-bit code range, " +
"Pi (\u03a0) and Sigma (\u03a3).";
Console.WriteLine("Original string:");
Console.WriteLine(unicodeString);
// Encode the string.
Byte[] encodedBytes = utf7.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 = utf7.GetString(encodedBytes);
Console.WriteLine();
Console.WriteLine("Decoded bytes:");
Console.WriteLine(decodedString);
}
}
using namespace System;
using namespace System::Text;
using namespace System::Collections;
int main()
{
// Create a UTF-7 encoding.
UTF7Encoding^ utf7 = gcnew UTF7Encoding;
// A Unicode string with two characters outside a 7-bit code range.
String^ unicodeString = L"This Unicode string contains two characters with codes outside a 7-bit code range, Pi (\u03a0) and Sigma (\u03a3).";
Console::WriteLine( "Original string:" );
Console::WriteLine( unicodeString );
// Encode the string.
array<Byte>^encodedBytes = utf7->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();
// Decode bytes back to string.
// Notice Pi and Sigma characters are still present.
String^ decodedString = utf7->GetString( encodedBytes );
Console::WriteLine();
Console::WriteLine( "Decoded bytes:" );
Console::WriteLine( decodedString );
}
import System.*;
import System.Text.*;
class UTF7EncodingExample
{
public static void main(String[] args)
{
// Create a UTF-7 encoding.
UTF7Encoding utf7 = new UTF7Encoding();
// A Unicode string with two characters outside a 7-bit code range.
String unicodeString = "This Unicode string contains two characters "
+ "with codes outside a 7-bit code range, "
+ "Pi (\u03a0) and Sigma (\u03a3).";
Console.WriteLine("Original string:");
Console.WriteLine(unicodeString);
// Encode the string.
ubyte encodedBytes[] = utf7.GetBytes(unicodeString);
Console.WriteLine();
Console.WriteLine("Encoded bytes:");
for(int iCtr = 0; iCtr < encodedBytes.length; iCtr++) {
ubyte b = encodedBytes[iCtr];
Console.Write("[{0}]", String.valueOf(b));
}
Console.WriteLine();
// Decode bytes back to string.
// Notice Pi and Sigma characters are still present.
String decodedString = utf7.GetString(encodedBytes);
Console.WriteLine();
Console.WriteLine("Decoded bytes:");
Console.WriteLine(decodedString);
} //main
} //UTF7EncodingExample
继承层次结构
System.Object
System.Text.Encoding
System.Text.UTF7Encoding
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