four type of life cycle in c#
1)page load
2)page init
3)page pre render
4)page unload

Process Request Method does following things:

1. Intialize the memory
2. Load the view state
3. Page execution and post back events
4. Rendering HTML content
5. Releasing the memory

Process Request Method executes set of events for page class .These are called as Page life cycle events.

Page Life Cycle Events

• Page_Init
  The server controls are loaded and initialized from the Web form's view state. This is the first step in a Web form's life cycle.
• Page_Load
  The server controls are loaded in the page object. View state information is available at this point, so this is where you put code to change control settings or display text on the page.
• Page_PreRender
  The application is about to render the page object.
• Page_Unload
  The page is unloaded from memory.
• Page_Disposed
  The page object is released from memory. This is the last event in the life of a page object.
• Page_Error
  An unhandled exception occurs.
• Page_AbortTransaction
  A transaction is aborted.
• Page_CommitTransaction
  A transaction is accepted.
• Page_DataBinding
  A server control on the page binds to a data source. 
• Process Request Method finally renders HTML Page

submitted by :
Rizwan Ashraf Ansari (NIIT South - Ex Delhi)