Question

I want to write javascript logic for the check box list asp.net control, that if some condition in check box selection is true then select all, else deselect all.
How to figure out this check uncheck and there value using javascript?

Answer 1

<div><input type="checkbox" class="checkall"> Check all</div>
    <div><input type="checkbox" class="check"> Checkbox</div>
    <div><input type="checkbox" class="check"> Checkbox</div>
    <div><input type="checkbox" class="check"> Checkbox</div>

    <select size="5" multiple="multiple" class="listbox">
      <option value="test1">test1</option>
      <option value="test1">test1</option>
      <option value="test1">test1</option>
      <option value="test1">test1</option>
      <option value="test1">test1</option>
    </select>


<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js" type="text/javascript"></script>
<script>
$(function () { // this line makes sure this code runs on page load
    $('.checkall').click(function () {
        $('.check').attr('checked', this.checked); //if you want to select/deselect checkboxes use this
        $('.listbox option').attr('selected', this.checked);//if you want to select/deselect options in list use this
    });
});
</script>

http://jsfiddle.net/fMk2e/