一，测试Demo

namespace 不同编码下的中英文字符大小
{
    class Program
    {
        static void Main(string[] args)
        {
            ShowCode();
        }

        private static void ShowCode() {

            string[] strArray = { "b","abc","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) //ASCII编码
                    {
                        buffer = Encoding.ASCII.GetBytes(str);
                        back = Encoding.ASCII.GetString(buffer, 0, buffer.Length);
                        mode = "ASCII";
                    }
                    else if(i==1)  //UTF8编码
                    {
                        buffer = Encoding.UTF8.GetBytes(str);
                        back = Encoding.UTF8.GetString(buffer, 0, buffer.Length);
                        mode = "UTF8";
                    }
                    else           //Unicode编码
                    {
                        buffer = Encoding.Unicode.GetBytes(str);
                        back = Encoding.Unicode.GetString(buffer, 0, buffer.Length);
                        mode = "Unicode";
                    }

                    Console.WriteLine("编码方式:{0} ;字符串:{1} ;长度:{2}", mode, str, buffer.Length);

                    Console.WriteLine("编码后的字节数组:");

                    for (int j = 0; j <=buffer.Length-1; j++)
                    {
                        Console.WriteLine("  "+buffer[j]+"  "); 
                    }

                    Console.WriteLine("\n编码后字符为:{0} \n",back);

                    
                }

                Console.WriteLine("----------------------------------------------------------");
            }
        
        }
    }
}

  二，结果如下

          

   b只有在Unicode下面编码为2字节，读到的byte[1]被编码为了0；ASCII码和UTF-8编码相同。

Unicode编码每个字节后面都补了个0；

对于中文：

ASCII码编码后连外星人都读不出来了；

UTF8编码出了3个字节；

Unicode出来了两个字节；