The more I use ASP.NET, the more if (!IsPostBack) {}
seems pointless...
First example:
For example, I just Googled an issue, they said use this as part of the solution:
if (!Page.IsPostBack)
{
Page.LoadComplete += new EventHandler(Page_LoadComplete);
}
Which does exactly as coded, LoadComplete will only fire on the first load. After clicking a button, or anything that triggers a postback, the LoadComplete event is left unhooked, thus skipping the event handler. Therefore, their "fix" only works upon the first load = worthless. I promptly commented out the if (!Page.IsPostBack) {}
and now the event always triggers as desired.
Second example:
I am attempting to hook events to a dynamically created button (which by the way, I can't get to work [GRR!]). I see examples showing this:
myEditToggleButton = new Button();
myEditToggleButton.ID = "editToggleButton";
//^GOTTA HAVE THIS FOR EVENTS TO WORK! (supposedly, I haven't seen it work...)
if (!IsPostBack)
{
myEditToggleButton.Click += new EventHandler(myEditToggleButton_Click);
}
Controls.Add(myEditToggleButton);
Like the first example, my understanding is that the event wouldn't be hooked after the first page load, thus the button is "inert" after one click (because clicking triggered a postback).
Question:
When should you use if (!IsPostBack) {}
? I am guessing it has to do with mark-up created controls only.
IsPostBack. Gets a value that indicates whether the page is being rendered for the first time or is being loaded in response to a postback. The IsPostBack property can be used to determine if the page is submitted to itself. When a form is submitted back to the same page that contains it, it's called a post back.
IsPostBack event is generated by the web controls to alert the server to take respected action of the event generated. When the button is clicked then click event is generated which further cause ispostback event & it alerts the server to take respected action during postback event.
IsPostBack is a property of the Asp.Net page that tells whether or not the page is on its initial load or if a user has perform a button on your web page that has caused the page to post back to itself.
IsPostBack is a Boolean property of a page when is set (=true) when a page is first loaded. Thus, the first time that the page loads the IsPostBack flag is false and for subsequent PostBacks, it is true.
In short, you use it everytime you need to execute something ONLY on first load.
The classic usage of Page.IsPostBack
is data binding / control initialization.
if(!Page.IsPostBack)
{
//Control Initialization
//Databinding
}
Things that are persisted on ViewState
and ControlState
don't need to be recreated on every postback so you check for this condition in order to avoid executing unnecessary code.
Another classic usage is getting and processing Querystring
parameters. You don't need to do that on postback.
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