1. Starter client method: A server side web method is being called from a client side method, that will be executed asynchronously (i.e. NO need to wait or halt for the user interface execution completion).
Along with the parameters of that web method, the client side method calls the method by adding another parameter with a client method name, that will be executed after the execution of the web method.
2. Server side web method: The server side web method will be executed asynchronously.
3. Callback client method: This is the client side method which has been specified by the starter client method while invoking the server side web method that has been executed asynchronously.
Return value of web method: The parameter of the call back method will contain the return value of the server side web method, which will be used by the call back method, to utilize the return value or the result in the client end.
Special Note:
# "PageMethods" is an Atlas utility class, by which we can call a method of the code-behind class of the caller page, without specifying the class name of the callee method class.
# Validation scenario: If we want to implement data validation we can invoke the server side method asynchronously, along with calling the web service data method. In that case the execution scenario will be:
1. Starter client method 2. Server side validation method (that will be executed asynchronously as well as) 3. Client side callback method for validation 4. Server side web method to perform actual data operation 5. Client side callback method to complete the execution scenario of actual data operation web method.