Determine if postback is page_load or itemcommand

Question

I've got a user list on the left side of my page in a datagrid and I want to load a div in the right side of my page with the clicked user's information. I assume I'll do the load of the div in the itemcommand event, but how do I handle page load then? Do I need to know what caused the postback? Do I need to reload the grid on page_load as well?

Answer 1

Exclude the grid binding with checking !IsPostBack

if(!IsPostBack){
   // Bind the Grid
}

For div itemcommand you get retrieve the value of which is clicked from grid and load the user's information.

So, you will not required to load the grid everytime. It will just load first time. I dont think you will required to check what cuased the postback, because anyway you will load grid once only.

Answer 2

how do I handle page load then?

Every postback uses a brand new instance of your page class, and completely rebuilds the page. The only thing that's different is that some controls might be pre-populated via ViewState. You don't need to repeat the load work for any of those controls.

Do I need to know what caused the postback?

ASP.Net will handle that for you and fire the event. You only need know whether it is a postback, and maybe not even that (see the next part).

Do I need to reload the grid on page_load as well?

Yes. Well, sort of. You need to re-render the html for the grid to the browser. The good news is odds are your grid data is already in viewstate and it will happen automatically. You don't need to worry about it yourself.

However, in many cases you may find that it's better to turn off viewstate for grids and reload them on each postback anyway. This is because ViewState is just a hidden input on your page that must be posted (uploaded) to the server with each request. Most internet users have very limited upload bandwidth, and so a large ViewState can make your site seem slugish, even if your server is hardly breaking a sweat.

Depending on your situation, you might do better by trading some excess server performance for site responsiveness by disabling ViewState on select controls. In this case, you will always load the grid and no longer need care whether or not a request is a postback.

By contrast, if this is an intranet application where users typically have local ethernet connections to your web server it's hard to beat ViewState for balancing responsiveness and server performance.