I have been thinking about doing this since I started using jQuery about a week ago because it is so much cleaner on the client side instead of having to do a postback just to select some CheckBoxes. Turns out it is pretty easy to do if you get your selectors right. Hint: FireBug makes this a lot easier.

  
Note: The ListView is based on an excellent post by Matt Berseth http://mattberseth.com/blog/2007/11/yui_datatable_styled_listview.html 

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Explanation:

When you add a CssClass to a CheckBox control, the class isn't applied to the checkbox, but instead to a span tag that surrounds the checkbox. With that in mind, you just have to select the spans in your code that have your CssClass applied and then look for a CheckBox in them.

So,

becomes this in the source:

So now all we have to do is find  the CheckBox that we want to act as our select all control and give it a click event. The click event will need to find all of the spans with our CssClass applied and then the CheckBoxes inside them. The jQuery I used to do this is below:

    $(document).ready(function() 
        { 
            $("#ListViewCustomers_CheckBoxSelectAllItems").click(function() 
            { 
                var checked_status = this.checked; 
                $("td >.selectAllItems >input:checkbox").each(function() 
                { 
                    this.checked = checked_status; 
                }); 
            }); 
                            
        });

I did run into a problem when I tried to throw my ListView into an UpdatePanel. It would work the first time until the panel was posted back, but after that it wouldn't work. It just took a client side pageLoad event to fix things up:

    function pageLoad()
    {
        $(document).ready(function() 
            { 
                $("#ListViewCustomers2_CheckBoxSelectAllInUpdatePanel").click(function() 
                { 
                    var checked_status = this.checked; 
                    $("td >.selectAllItemsInUpdatePanel >input:checkbox").each(function() 
                    { 
                        this.checked = checked_status; 
                    }); 
                }); 
                                
            });    
    }

Hope this helps someone. Please let me know if you use it and make improvements.