单项选择题 You create a Microsoft ASP.NET application by using the Microsoft .NET Framework version 3.5. You derive a new validation control from the BaseValidator class.  The validation logic for the control is implemented in the Validate method in the following manner：   protected static bool Validate（string value）   {   // ...   }    You need to override the method that validates the value of the related control.  Which override method should you use？（）

单项选择题 You create a Microsoft ASP.NET application by using the Microsoft .NET Framework version 3.5. You create a custom control named OrderForm. You write the following code segment：   public delegate void CheckOrderFormEventHandler（EventArgs e）； private static readonly object CheckOrderFormKey = new object（）；   public event CheckOrderFormEventHandler CheckOrderForm   {   add { Events.AddHandler（CheckOrderFormKey， value）； }  remove { Events.RemoveHandler（CheckOrderFormKey， value）； }  }    You need to provide a method that enables the OrderForm control to raise the CheckOrderForm event.  Which code segment should you use？（）

单项选择题 You are the senior technician at Certkiller.com. You have been instructed to create a MicrosoftASP.NET application using Microsoft .NET Framework v3.5.  You make use of ASP.NET AJAX to create a web form. In order to handle exception from asynchronous postbacks you decide to write the client script code fragment below. You write thefollowing client-script code fragment to handle the exceptions thrown from asynchronouspostbacks. （The line numbers is included for reference purposes） 01 <script type="text/javascript"> 02 function pageLoad（） 03 { 04  var pageMgr = Sys.WebForms.PageRequestManager.getInstance（）； 05 06 } 07 08 function errorHandler（sender， args） 09 { 10 11 } 12 </script>  You receive an instruction from the network administrator to ensure that the application is able toexecute the criteria below： * You need to ensure that the application makes use of a common client-script function namederrorHandler. * The Label control with an ID named TestError should be updated with the error message.* The browser should not display any message box or Javascript error  How can this be accomplished？（）