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,0,bytedata.Length);