ถ้าต้องการเขียนโค้ดเช็ค นามสกุล ผมต้องเพิ่มตัวไหนลงไปบรรทัดไหนอ่ะคับ รบกวนหน่อย

 protected void btnRegister_Click(object sender, EventArgs e)
        {

            SqlConnection objConn = new SqlConnection();
            SqlCommand objCmd = new SqlCommand();
            String strConnString, strSQL;
            //StringBuilder strSQL =default(StringBuilder);

            int intCount = 0;

            //*** Open Connection ***'
            strConnString = "Data Source=NEWPROGRAMMER;Initial Catalog=customer;Integrated Security=True";
            objConn = new SqlConnection();
            objConn.ConnectionString = strConnString;
            objConn.Open();


            strSQL = "INSERT INTO register (username,lastname,password,address,tel,mobile,email) " +
            " VALUES " +
            " ('" + this.txtUsername.Text + "','" + this.txtLastname.Text + "','"+ EncMD5("'" + this.txtPassword.Text + "'") +"', " +
            " '" + this.txtAddress.Text + "','" + this.txtTel.Text + "','" + this.txtMobile.Text + "','" + this.txtEmail.Text +"' )";
            
            objCmd.Connection = objConn;
            objCmd.CommandText = strSQL;
            objCmd.CommandType = CommandType.Text;
            this.pnlRegister.Visible = false;

            try
            {
                objCmd.ExecuteNonQuery();
                this.lblStatus.Text = "Record Inserted";
                this.lblStatus.Visible = true;
                //เพิ่ม
               // Response.Redirect("index.aspx");
            }
            catch (Exception ex)
            {
                this.lblStatus.Visible = true;
                this.lblStatus.Text = "Record can not insert Error (" + ex.Message + ")";
            }
            objConn.Close();
            objConn = null;

            this.pnlFinish.Visible = true;
            Response.Write("<Script language=javascript> alert('คุณทำการ Register เรียบร้อยแล้วรอ Approve จากผู้ดูแลระบบ');window.location = 'index.aspx';</Script>");           
       
            //** Check Lastname **//


            strSQL = "SELECT COUNT (*) FROM register WHERE lastname = '" + lblLastname.Text + "' ";
            objCmd = new SqlCommand(strSQL, objConn);
            objCmd.ExecuteNonQuery();

            if (intCount >=1)
            {
                this.lblLastname.Text = "Lastname already exists!!";
                return;
            }

            //**End Check Lastname **//

            objConn.Close();
            objConn = null;
        }

 strSQL = "SELECT COUNT (*) FROM register WHERE lastname = '" + lblLastname.Text + "' ";
            objCmd = new SqlCommand(strSQL, objConn);

 strSQL = new StringBuilder();
            strSQL.Append(" SELECT COUNT(*) FROM member ");
            strSQL.Append(" WHERE Username = @sUsername ");
            objCmd = new SqlCommand(strSQL.ToString(), objConn);
            objCmd.Parameters.Add("@sUsername", SqlDbType.VarChar).Value = this.txtUsername.Text;
            intCount = (int)objCmd.ExecuteScalar();