How to capture submit event using jQuery in an ASP.NET application?

Thanks, @Ken Browning and @russau for pointing me in the direction of hijacking __doPostBack. I've seen a couple of different approaches to this:

1. Hard-code my own version of __doPostBack, and put it later on the page so that it overwrites the standard one.
2. Overload Render on the page and inject my own custom code into the existing __doPostBack.
3. Take advantage of Javascript's functional nature and create a hook for adding functionality to __doPostBack.

The first two seem undesirable for a couple of reasons (for example, suppose in the future someone else needs to add their own functionality to __doPostBack) so I've gone with #3.

This addToPostBack function is a variation of a common pre-jQuery technique I used to use to add functions to window.onload, and it works well:

addToPostBack = function(func) {
    var old__doPostBack = __doPostBack;
    if (typeof __doPostBack != 'function') {
        __doPostBack = func;
    } else {
        __doPostBack = function(t, a) {
            if (func(t, a)) old__doPostBack(t, a);
        }
    }
};

$(document).ready(function() {
    alert("Document ready.");
    addToPostBack(function(t,a) {
        return confirm("Really?")
    });
});

Edit: Changed addToPostBack so that

1. it can take the same arguments as __doPostBack
2. the function being added takes place before __doPostBack
3. the function being added can return false to abort postback

I've had success with a solution with overriding __doPostBack() so as to call an override on form.submit() (i.e. $('form:first').submit(myHandler)), but I think it's over-engineered. As of ASP.NET 2.0, the most simple workaround is to:

1. Define a javascript function that you want to run when the form is submitted i.e.

   <script type="text/javascript">
   
   function myhandler()
   {
       alert('you submitted!');
   }
   
   </script>
   

2. Register your handler function within your codebehind i.e.

   protected override void OnLoad(EventArgs e)
   {
       base.OnLoad(e);
       ScriptManager.RegisterOnSubmitStatement(Page, Page.GetType(), 
                                               "myHandlerKey", "myhandler()");
   }
   

That's all! myhandler() will be called from straightforward button-input submits and automatic __doPostBack() calls alike.

Yeah, this is annoying. I replace __doPostBack with my own so that I could get submit events to fire.

Iirc, this is an issue when submitting a form via javascript (which calls to __doPostBack do) in IE (maybe other browsers too).

My __doPostBack replacement calls $(theForm).submit() after replicating the default behavior (stuffing values in hidden inputs)

I don't know how to do it with jQuery, but you could add an OnClientClick property to the ASP.NET control:

<asp:linkbutton id="TestButton" text="Click me!" runat="server" OnClientClick="alert('Submit detected.');" />