ทำ RequiredFieldValidator เช็ค username ว่ามันตรงกับ username ในฐานข้อมูลรึป่าว

            SqlConnection objConn = null;
            string strConnString = null;
            StringBuilder strSQL = default(StringBuilder);
            SqlCommand objCmd = null;
            int intCount = 0;

            //*** Open Connection ***'
            strConnString = "Server=localhost;UID=sa;PASSWORD=;database=mydatabase;Max Pool Size=400;Connect Timeout=600;";
            objConn = new SqlConnection();
            objConn.ConnectionString = strConnString;
            objConn.Open();

            //*** Check Username exists ***'
            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();
            if (intCount >= 1)
            {
                this.lblStatus.ForeColor = System.Drawing.Color.Red;
                this.lblStatus.Text = "Username already exists!!";
                return;
            }