Ajax Validation Username ช่วยทีคับ จะตรวจสอบทันทีว่า User ชื่อที่กรอกไม่ซ้ำกันกับชื่อในฐานข้อมูล

<asp:ScriptManager ID="ScriptManager1" runat="server" EnablePageMethods="true" />

<asp:Label ID="lblUserName" runat="server" AssociatedControlID="UserName">Desired Username</asp:Label>
<asp:TextBox ID="UserName" runat="server" Class="inputbox" onkeyup="usernameChecker(this.value);"
                                Text='<%# Bind("UserName") %>'></asp:TextBox>
<span id="spanAvailability"></span>

          <script type="text/javascript">
                    var usernameCheckerTimer;
                    var spanAvailability = $get("spanAvailability");

                     function usernameChecker(UserName) 
                          {
                                  clearTimeout(usernameCheckerTimer);
                                  if (UserName.length == 0)
                                        spanAvailability.innerHTML = "";
                                  else 
                                      {
                                        spanAvailability.innerHTML = "<span style='color: #ccc;'>checking...</span>";
                                        usernameCheckerTimer = setTimeout("checkUsernameUsage('" + UserName + "');", 750);
                                      }
                         }


                     function checkUsernameUsage(UserName) 
                               {
                                    // initiate the ajax pagemethod call
                                    // upon completion, the OnSucceded callback will be executed
                                    PageMethods.IsUserAvailable(UserName, OnSucceeded);
                                }

                                // Callback function invoked on successful completion of the page method.


                     function OnSucceeded(result, userContext, methodName) 
                               {
                                    if (methodName == "IsUserAvailable") 
                                       {
                                             if (result == true)
                                            spanAvailability.innerHTML = "<span style='color: DarkGreen;'>Available</span>";
                                        else
                                            spanAvailability.innerHTML = "<span style='color: Red;'>Unavailable</span>";
                                        }
                                }
          </script>

    public static bool IsUserAvailable(string UserName)
    {
        MembershipUser usr = Membership.GetUser(UserName);
        return (usr == null);
    }