[转载] 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);
        }
    }
}

程序输出为：

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。