ASP.Net

Web Form Life Cycle
Every request for a page made to a web server causes a chain of events at the server. These events, from beginning to end, constitute the life cycle of the page and all its components. The life cycle begins with a request for the page, which causes the server to load it. When the request is complete, the page is unloaded. From one end of the life cycle to the other, the goal is to render appropriate HTML output back to the requesting browser. The life cycle of a page is marked by the following events, each of which you can handle yourself or leave to default handling by the ASP.NET server:

1. Initialize
Initialize is the first phase in the life cycle for any page or control. It is here that any settings needed for the duration of the incoming request are initialized.

2. Load ViewState
The ViewState property of the control is populated. The ViewState information comes from a hidden variable on the control, used to persist the state across round trips to the server. The input string from this hidden variable is parsed by the page framework, and the ViewState property is set. This can be modified via the LoadViewState( ) method. This allows ASP.NET to manage the state of your control across page loads so that each control isn't reset to its default state each time the page is posted.

3. Process Postback Data
During this phase, the data sent to the server in the posting is processed. If any of this data results in a requirement to update the ViewState, that update is performed via the LoadPostData( ) method.

4. Load
CreateChildControls( ) is called, if necessary, to create and initialize server controls in the control tree. State is restored, and the form controls contain client-side data. You can modify the load phase by handling the Load event with the OnLoad() method.

5. Send Postback Change Modifications
If there are any state changes between the current state and the previous state, change events are raised via the RaisePostDataChangedEvent( ) method.

6. Handle Postback Events
The client-side event that caused the postback is handled.

7. PreRender
This is your last chance to modify the output prior to rendering using the OnPreRender( ) method.

8. Save State
Near the beginning of the life cycle, the persisted view state was loaded from the hidden variable. Now it is saved back to the hidden variable, persisting as a string object that will complete the round trip to the client. You can override this using the SaveViewState( ) method.

9. Render
This is where the output to be sent back to the client browser is generated. You can override it using the Render method. CreateChildControls( ) is called, if necessary, to create and initialize server controls in the control tree.

10. Dispose
This is the last phase of the life cycle. It gives you an opportunity to do any final cleanup and release references to any expensive resources, such as database connections. You can modify it using the Dispose( ) method.


What is the purpose of Server.MapPath method in Asp.Net?
In Asp.Net Server.MapPath method maps the specified relative or virtual path to the corresponding physical path on the server. Server.MapPath takes a path as a parameter and returns the physical location on the hard drive. Syntax

Suppose your Text files are located at D:\project\MyProject\Files\TextFiles

If the root project directory is MyProject and the aspx file is located at root then to get the same path use code

//Physical path of TextFiles
string TextFilePath=Server.MapPath("Files/TextFiles");

What is the use of Master Pages in Asp.Net?
A master page in ASP.Net provides shared HTML, controls, and code that can be used as a template for all of the pages of a website.
Every master page has asp:contentplaceholder control that will be filled by the content of the pages that use this master page.
You can create a master page that has header and footer i.e. a logo, an image, left navigation bar etc and share this content on multiple pages. You need not to put these things on every aspx page.

What are the different state management techniques used in asp.net for web applications?
In ASP.Net the state can be maintained in following ways
Server-side state management
Application objects
Session Variables
Database
Client-side state management
Cookies
Hidden input fields
Query String
ViewState