ASP .NET Page Life Cycle Events

When a page request is send to a web server, the page tuns through a series of events during its creation and disposal.
Here are some important ASP .NET page life cycle events.

1) PreInit 
The entry point of the page life cycle is the pre-initialization phase called "PreInit". This is the only event where programmatic access to master pages and themes is allowed.  You can dynamically set the values of master pages and themes in this event.  You can also dynamically create controls in this event.

2) Init
This event fires after each control has been initialized. You can use this event to change initialization values for controls. The "Init" event is fired first for the most bottom control in the hierarchy, and then fired up the hierarchy until it is fired for the page itself.

3) Load
The Load event fired after the Init event. Code inside the page load event typically checks for PostBack and then sets control properties appropriately. This method is typically used for most code, since this is the first place in the page lifecycle that all values are restored. Most code checks the value of IsPostBack to avoid unnecessarily resetting state. You may also wish to call Validate and check the value of IsValid in this method. You can also create dynamic controls in this method.

4) PostBack event handling
If the request is a postback, control event handlers are called. After that, the Validate method of all validator controls is called, which sets the IsValid property of individual validator controls and of the page. (There is an exception to this sequence: the handler for the event that caused validation is called after validation.)

5) Render
This is a method of the page object and its controls (and not an event). At this point, ASP.NET calls this method on each of the page's controls to get its output. The Render method generates the client-side HTML, Dynamic Hypertext Markup Language (DHTML), and script that are necessary to properly display a control at the browser.

Note: Right click on the web page displayed at client's browser and view the Page's Source. You will not find any aspx server control in the code. Because all aspx controls are converted to their respective HTML representation. Browser is capable of displaying HTML and client side scripts.

6) Unload
The Unload event is raised after the page has been fully rendered, sent to the client, and is ready to be discarded. At this point, page properties such as Response and Request are unloaded and cleanup is performed.

Note that these are the general page life-cycle events. There are some more events like:(Init complete, PreLoad, LoadComplete etc)which you can easily find on the internet. But these six events are the basic and most important events that you must have some knowledge about.