What is Asp.Net Page Life Cycle

What is Asp.Net Page Life Cycle?

Asp.Net   is a powerful platform for building Web applications.  The ASP.NET page life cycle is a good example to explore so you know how and when page elements are loaded and corresponding events are fired. When a page is requested, it is loaded into the server memory, processed and sent to the browser. Then it is unloaded from the memory. At each of this steps, methods and events are available, which could be overridden according to the need of the application.

The page life cycle phases are:

1.    Page Initialization (Initialization theme and master page)

a.    Page_PreInit

b.    Page_Init

c.    Page_InitComplete

2.    Page Load (load all control Button,TextBox)

a.    Page_PreLoad

b.    Page_Load

c.    Page_LoadComplete

3.    Page Render (convert server side to client side (html))

                                          i.    Page_Prerender

                                         ii.    Page_PreRenderComplete

                                        iii.    Page_SaveStateComplete

4.    Page Unload (processing destroyed after output)

·         Page_UnLoading

1.    Page_PreInit . PreInit is the first event in page life cycle. means this is the entry point of the ASP.NET page life cycle - it is the pre-initialization, so you have access to the page before it is initialized. Controls can be created within this event. Also, master pages and themes can be accessed. You can check the IsPostBack property here to determine if it is the first time a page has been loaded.

2.    Page_Init . Init event initializes the control property and the control tree is built. This event can be handled by overloading the OnInit method or creating a Page_Init handler. This event fires when all controls on the page have been initialized and skin settings have been applied.

3.    Page_InitComplete . InitComplete event allows tracking of view state. This event fires once all page and control initializations complete. This is the last event fired where ViewState is not set, so ViewState can be manipulated in this event.

4.    Page_PreLoad . This event is triggered before the post back data is loaded in the controls. This event can be handled by overloading the OnPreLoad method or creating a Page_PreLoad handler

5.    Page_Load . the Load event is raised for the page first and then recursively for all child controls. The controls in the control tree are created. This event can be handled by overloading the OnLoad method or creating a Page_Load handler.

6.    Page_LoadComplete . the loading process is completed, control event handlers are run and page validation takes place. This event can be handled by overloading the OnLoadComplete method or creating a Page_LoadComplete handler.

7.    Page_PreRender . the PreRender event occurs just before the output is rendered. By handling this event, pages and controls can perform any updates before the output is rendered.

8.    Page_PreRenderComplete . as the PreRender event is recursively fired for all child controls, this event ensures the completion of the pre-rendering phase.

9.    Page_SaveStateComplete . state of control on the page is saved. Personalization, control state and view state information is saved. The HTML markup is generated. This stage can be handled by overriding the Render method or creating a Page_Render handler.

10. Page_UnLoad . This event fires for each control and then the page itself. It is fired when the HTML for the page is fully rendered. This is where you can take care of cleanup tasks, such as properly closing and disposing database connections.. 

Example  with Page Life Cycle in Asp.net.........................

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.UI;

using System.Web.UI.WebControls;

public partial class _Default : System.Web.UI.Page

{

protected void Page_PreInit(object sender, EventArgs e)

{

Response.Write("<i><b><font color='red'> 1. </font></b></i>   Page PreInit <br/>");

}

protected void Page_Init(object sender, EventArgs e)

{

Response.Write("<i><b><font color='red'> 2. </font></b></i> Page Init <br/>");

}

protected void Page_InitComplete(object sender, EventArgs e)

{

Response.Write("<i><b><font color='red'> 3. </font></b></i> Page PreInit Complete </br>");

}

protected void Page_PreLoad(object sender, EventArgs e)

{

Response.Write("<i><b><font color='Green'> 4. </font></b></i>  Page PreLoad </br>");

}

protected void Page_Load(object sender, EventArgs e)

{

Response.Write("<i><b><font color='Green'> 5. </font></b></i>Page Load <br/>");

}

protected void Page_LoadComplete(object sender, EventArgs e)

{

Response.Write("<i><b><font color='Green'> 6. </font></b></i> Page Load Complete </br>");

}

protected void Page_Prerender(object sender, EventArgs e)

{

Response.Write("<i><b><font color='Blue'> 7. </font></b></i> Page PreRender</br>");

}

protected void Page_PreRenderComplete(object sender, EventArgs e)

{

Response.Write("<i><b><font color='Blue'> 8. </font></b></i> Page PreRender Complete</br>");

}

protected void Page_SaveStateComplete(object sender, EventArgs e)

{

Response.Write("<i><b><font color='Blue'> 9. </font></b></i> Page SaveState Complete</br>");

}

 protected void Button1_Click(object sender, EventArgs e)

{

Response.Write("<i><b><font color='Grey'> 10. </font></b></i> Button Click </br>");

}

protected void Page_UnLoading(object sender, EventArgs e)

{

Response.Write("<i><b><font color='Pink'> 11. </font></b></i> Page Unloading Event </br>");

}

 }