string strPath =  "aHR0cDovLzIwMy44MS4yOS40Njo1NTU3L1

9iYWlkdS9yaW5ncy9taWRpLzIwMDA3MzgwLTE2Lm1pZA==";

    byte[] bpath = Convert.FromBase64String(strPath);

    strPath = System.Text.ASCIIEncoding.Default.GetString(bpath);

  System.Text.Encoding encode = System.Text.Encoding.ASCII ;

    byte[]  bytedata = encode.GetBytes( "test");

    string strPath = Convert.ToBase64String(bytedata,,bytedata.Length);