附录：ASCII、UTF8、Uncicode 编码下的中英文字符大小

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 = 0; i <= 2; i++) { 
 if (i == 0) { 
 buffer = Encoding.ASCII.GetBytes(str); 
 back = Encoding.ASCII.GetString(buffer, 0, buffer.Length); 
 mode = "ASCII"; 
 } else if (i == 1) { 
 buffer = Encoding.UTF8.GetBytes(str); 
 back = Encoding.UTF8.GetString(buffer, 0, buffer.Length); 
 mode = "UTF8"; 
 } else { 
 buffer = Encoding.Unicode.GetBytes(str); 
 back = Encoding.Unicode.GetString(buffer, 0, buffer.Length); 
 mode = "Unicode"; 
 } 
 Console.WriteLine("Mode: {0}, String: {1}, Buffer.Length: {2}", 
 mode, str, buffer.Length); 
 Console.WriteLine("Buffer:"); 
 for (int j = 0; j <= buffer.Length - 1; j++) { 
 Console.Write(buffer[j] + " "); 
 } 
 Console.WriteLine("\nRetrived: {0}\n", back); 
 } 
 } 
}

输出为：

Mode: ASCII, String: b, Buffer.Length: 1 
Buffer: 98 
Retrived: b 
Mode: UTF8, String: b, Buffer.Length: 1 
Buffer: 98 
Retrived: b 
Mode: Unicode, String: b, Buffer.Length: 2 
Buffer: 98 0 
Retrived: b 
Mode: ASCII, String: abcd, Buffer.Length: 4 
Buffer: 97 98 99 100 
Retrived: abcd 
Mode: UTF8, String: abcd, Buffer.Length: 4 
Buffer: 97 98 99 100 
Retrived: abcd 
Mode: Unicode, String: abcd, Buffer.Length: 8 
Buffer: 97 0 98 0 99 0 100 0 
Retrived: abcd 
Mode: ASCII, String: 乙, Buffer.Length: 1 
Buffer: 63 
Retrived: ? 
Mode: UTF8, String: 乙, Buffer.Length: 3 
Buffer: 228 185 153 
Retrived: 乙
Mode: Unicode, String: 乙, Buffer.Length: 2 
Buffer: 89 78 
Retrived: 乙
Mode: ASCII, String: 甲乙丙丁, Buffer.Length: 4 
Buffer: 63 63 63 63 
Retrived: ???? 
Mode: UTF8, String: 甲乙丙丁, Buffer.Length: 12 
Buffer: 231 148 178 228 185 153 228 184 153 228 184 129 
Retrived: 甲乙丙丁
Mode: Unicode, String: 甲乙丙丁, Buffer.Length: 8 
Buffer: 50 117 89 78 25 78 1 78 
Retrived: 甲乙丙丁

大体上可以得出这么几个结论：

• 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。