C# HmacMD5 加密

string HmacMD5(string source, string key)
       {
           HMACMD5 hmacmd = new HMACMD5(Encoding.Default.GetBytes(key));
           byte[] inArray = hmacmd.ComputeHash(Encoding.Default.GetBytes(source));
           StringBuilder sb = new StringBuilder(); 

           for (int i = ; i < inArray.Length; i++)
           {
               sb.Append(inArray[i].ToString("X2"));
           } 

           hmacmd.Clear(); 

           return sb.ToString();
       } 

需 引用命令空间System.Security.Cryptography