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ASP.Net: Page_Load() being called multiple times

Answer 1

+1 A:

When the page posts back, the Page_Load method is called. Then, once the server actually processes the page and sends you a new one based on changes, the Page_Load is called again, actually the first time on the new page sent to you.

So if you are pulling data in the Page_Load event or setting some values, enclose it in the following block:

if(!Page.IsPostBack)
{

}

to preserve some of your state. Otherwise, the instructions that you put into the Page_Load event will execute every time.

It helps to review the ASP.Net page lifecycle :)

Eugene 2009-07-07 21:25:59

Answer 2

+11 A:

Remember, in ASP.Net every time you cause a postback of any kind, including handling events like button clicks, you're working with a brand new instance of your page class that must be rebuilt from scratch. Any work you've done previously to build the page on the server is gone. That means running the entire page life cycle, including your page load code, and not just the click code.

Always two there are, no more, no less. A request and a response.

Joel Coehoorn 2009-07-07 21:26:01

guhhh so instance variables are useless? this is weird because I did the exact same stuff elsewhere in the webpage and they work fine, i didn't happen to hit re-instantation there somehow i guess.

evilfred 2009-07-07 21:27:00

Instance variables are useful for holding data in between events in the same postback. For example, you could open an sql connection early and use that same connection later in the life cycle. Where instance variables work elsewhere across postbacks you're likely relying on ViewState.

Joel Coehoorn 2009-07-07 21:30:25

+1 for thinking about the *most obvious* thing first rather than going through more advanced speculations!

Mehrdad Afshari 2009-07-07 21:32:46

+1 for not only being the right answer, but throwing in an appropriate Star Wars reference.

Adrien 2009-07-07 21:33:26

Another way to remember this is that instance variables represent the "state" of your page class (or any class), and the web is stateless.

Joel Coehoorn 2009-07-07 21:33:59

You can use instance variables as long as it's during a single Request. Once the page is served to the user and they click a button, that's a second request with its own instance variables.State management in ASP.net is a whole can of worms, but you need to deal with it to do anything. http://www.exforsys.com/tutorials/asp.net/managing-state-with-asp.net-and-csharp.html

Greg 2009-07-07 21:34:22

If you want to persist your instance variables between postback, you can store them in the ViewStatepublic int MyVal{ get{ return (int)ViewState["__MyVal__"];} set{ ViewState["__MyVal__"] = value; }}

Babak Naffas 2009-07-07 21:37:28

Answer 3

A:

Just a shot in the dark but maybe add this after your page_load:

if (!IsPostBack)
{

Tim Meers 2009-07-07 21:26:46

Answer 4

+1 A:

As Joel mentioned, instance variables will be lost once the page is sent back to the client. However, there are various methods of storing the values of your variables so you can retrieve them later. This page on State Management is a good starting point if you want to learn more.

tbreffni 2009-07-07 21:47:21

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ASP.Net: Page_Load() being called multiple times

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