whats wrong in this asp.net webusercontrol code?

You don't need #<%=chkAll.ClientID %> for controls that don't have runat="server" Just use the ID.

It looks like you're trying to do exactly what's being demonstrated here. From that demo:

$(document).ready(function()
{
  $("#paradigm_all").click(function()               
  {
    var checked_status = this.checked;
    $("input[@name=paradigm]").each(function()
    {
      this.checked = checked_status;
    });
  });                   
});

Note the key differences between what this is doing and what your code is doing. You are selecting inputs of type button and trying to change a property on them called click. That... won't work. This demo is instead selecting some inputs of type checkbox by name and setting their checked status. Additionally, it's doing it by use of a checkbox rather than a button (which appears to be your stated intention).

You can read up on jQuery selectors here. There's a lot you can use for selecting elements. In the demo, the elements have the same name attribute and can be selected as such. You should be able to set name properties in your .NET server controls for use on client-side code just as easily. Without name attributes, you could alternatively select them child elements of your Panel, or your div, etc. You may want to give some names or ids in there just to make it easy on yourself.

Edit: Based on your comment, you can just change the logic a little bit. You'd still bind to the click event as before. However, you wouldn't be able to use the elements own checked status, since a button doesn't have one. Something like this, for example:

$(document).ready(function()
{
  $("#paradigm_all").click(function()                
  {
    $(":checkbox").each(function()
    {
      this.checked = true;
    });
  });                    
});

This modifies the logic of the previous example (assuming you've changed the target checkbox to a button in the markup). The main differences are:

• The selector for the other checkboxes now selects all checkboxes on the page. You'll probably want to target a more specific selector than this, but it works for the purpose of the demo.
• The button only sets all checkboxes to checked. With this example, clicking the button again doesn't un-check them. To accomplish that you'd have to define a bit more logic. For example, if some of them are checked and the button is clicked, do they all check or all un-check? Or do they toggle? What if the user uses the button to check all and then un-checks one? Upon clicking the button again, does the one get re-checked or do the rest get un-checked? Lots of UX questions :)