using System;
using System.Text;
    
namespace ConvertExample
{
   class ConvertExampleClass
   {
      static void Main()
      {
         string unicodeString = "This string contains the unicode character Pi(\u03a0)";
    
         // Create two different encodings.
         Encoding ascii = Encoding.ASCII;
         Encoding unicode = Encoding.Unicode;
    
         // Convert the string into a byte[].
         byte[] unicodeBytes = unicode.GetBytes(unicodeString);
    
         // Perform the conversion from one encoding to the other.
         byte[] asciiBytes = Encoding.Convert(unicode, ascii, unicodeBytes);
            
         // Convert the new byte[] into a char[] and then into a string.
         // This is a slightly different approach to converting to illustrate
         // the use of GetCharCount/GetChars.
         char[] asciiChars = new char[ascii.GetCharCount(asciiBytes, 0, asciiBytes.Length)];
         ascii.GetChars(asciiBytes, 0, asciiBytes.Length, asciiChars, 0);
         string asciiString = new string(asciiChars);
    
         // Display the strings created before and after the conversion.
         Console.WriteLine("Original string: {0}", unicodeString);
         Console.WriteLine("Ascii converted string: {0}", asciiString);
      }
   }
}

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 方法执行实际的解码。

如果要转换的数据仅存在于连续块（如从流中读取的数据）中，或者数据量很大，需要划分为较小的块，则可使用由某个派生类的 GetDecoder 方法提供的 Decoder 或由派生类的 GetEncoder 方法提供的 Encoder。