tailieunhanh - Beginning Ajax with ASP.NET- P13

Beginning Ajax with P13:Thank you for purchasing Beginning Ajax with . We know that you have a lot of options when selecting a programming book and are glad that you have chosen ours. We’re sure you will be pleased with the relevant content and high quality you have come to expect from the Wrox Press line of books. | Chapter 6 The 1 placeholder represents the WebForm_InitCallback JavaScript code which collects and prepares the form data to post to the server for the callback to the server to be correctly interpreted and trapped by the runtime engine. This is crucial so that the correct server-side methods are executed in response to the callback event as expected. Finally the 2 placeholder represents the code this arg MyControl_Callback null This code should look familiar and is the same method used to obtain a callback event reference in the initial page-centric examples detailed previously in the discussion of the ICallbackEventHandler interface. It is used for exactly the same purpose here as the final step to initiate the asynchronous callback request to the server. To summarize the implementation of the iCallbackContainer method first constructs the arguments to send to the server-side callback request and returns a JavaScript block that first clears the posted data initializes the collection of the posted data in the HTTP request via WebForm_InitCallback and finally initiates the callback request by obtaining the callback event through the method. This section is not intended as a complete discussion on the specifics of implementing asynchronous callback functionality within your custom controls but merely serves as an introduction on how to begin such a task with asynchronous callbacks in mind. The reader is encouraged to perform further investigation in this advanced topic area and in particular in the creation of custom controls. Summary This chapter has introduced the concept of Asynchronous Callback Client Scripts that are provided with . This feature allows a developer to utilize Ajax-like functionality within in a number of ways. You looked at how you could include asynchronous callbacks in your applications by Using out-of-the-box server controls that come .