转载>>ASCII、UTF8、Uncicode编码下的中英文字符大小

原地址：http://www.tracefact.net/CSharp-Programming/Network-Programming-Part2.aspx

ASCII、UTF8、Uncicode编码下的中英文字符大小

• ASCII不能保存中文

• UTF8是变长编码。在对ASCII字符编码时，UTF更省空间，只占1个字节，与ASCII编码方式和长度相同；Unicode在对ASCII字符编码时，占用2个字节，且第2个字节补零。

• UTF8在对中文编码时需要占用3个字节；Unicode对中文编码则只需要2个字节。

代码示例：

 private static void ShowCode() {
     string[] strArray = { "b", "abcd", "乙", "甲乙丙丁" };
     byte[] buffer;
     string mode, back;

     foreach (string str in strArray) {

         for (int i = ; i <= ; i++) {
             if (i == ) {
                 buffer = Encoding.ASCII.GetBytes(str);
                 back = Encoding.ASCII.GetString(buffer, , buffer.Length);
                 mode = "ASCII";
             } else if (i == ) {
                 buffer = Encoding.UTF8.GetBytes(str);
                 back = Encoding.UTF8.GetString(buffer, , buffer.Length);
                 mode = "UTF8";
             } else {
                 buffer = Encoding.Unicode.GetBytes(str);
                 back = Encoding.Unicode.GetString(buffer, , buffer.Length);
                 mode = "Unicode";
             }

             Console.WriteLine("Mode: {0}, String: {1}, Buffer.Length: {2}",
                 mode, str, buffer.Length);

             Console.WriteLine("Buffer:");
             for (int j = ; j <= buffer.Length - ; j++) {
                 Console.Write(buffer[j] + " ");
             }

             Console.WriteLine("\nRetrived: {0}\n", back);
         }
     }
 }

运行结果：

 Mode: ASCII, String: b, Buffer.Length:
 Buffer:
 Retrived: b

 Mode: UTF8, String: b, Buffer.Length:
 Buffer:
 Retrived: b

 Mode: Unicode, String: b, Buffer.Length:
 Buffer:
 Retrived: b

 Mode: ASCII, String: abcd, Buffer.Length:
 Buffer:
 Retrived: abcd

 Mode: UTF8, String: abcd, Buffer.Length:
 Buffer:
 Retrived: abcd

 Mode: Unicode, String: abcd, Buffer.Length:
 Buffer:
 Retrived: abcd

 Mode: ASCII, String: 乙, Buffer.Length:
 Buffer:
 Retrived: ?

 Mode: UTF8, String: 乙, Buffer.Length:
 Buffer:
 Retrived: 乙

 Mode: Unicode, String: 乙, Buffer.Length:
 Buffer:
 Retrived: 乙

 Mode: ASCII, String: 甲乙丙丁, Buffer.Length:
 Buffer:
 Retrived: ????

 Mode: UTF8, String: 甲乙丙丁, Buffer.Length:
 Buffer:
 Retrived: 甲乙丙丁

 Mode: Unicode, String: 甲乙丙丁, Buffer.Length:
 Buffer:
 Retrived: 甲乙丙丁

得出结论：

 ASCII不能保存中文(貌似谁都知道=_-`)。
 UTF8是变长编码。在对ASCII字符编码时，UTF更省空间，只占1个字节，与ASCII编码方式和长度相同；Unicode在对ASCII字符编码时，占用2个字节，且第2个字节补零。
 UTF8在对中文编码时需要占用3个字节；Unicode对中文编码则只需要2个字节。