This section describes using the method callback interfaces of this toolkit which includes the wwMethodCallback server control which makes it real easy to create code that calls class methods in server side code and return the results back to the client as JSON.

A number of mechanisms are available for calling server methods from the client:

• wwMethodCallbackMethod server control
  
• wwCallbackMethod client class
  
• ajaxJSON() client function for direct one line of code calls
  
• Raw AJAX callbacks using any AJAX library
  

On the server you can choose to implement callback methods in:

• Page Methods using [CallbackMethod] Attributes
  
• In custom and user controls using [CallbackMethod] Attributes
  
• HttpHandler deriving from wwCallbackHandler
  

The following topics are discussed here:

• Basic Page Callbacks using wwMethodCallback
• Passing Complex Objects in Callbacks
• Implementing Callback Methods on Custom or User Controls
• Using an wwCallbackHandler HttpHandler for optimized Callbac
• Using wwCallbackHandler with REST Calls