title: javascript to select all checkbox in gridview
body: <p>i am searching for the javascript that performs select all - deselect all feature in asp.net gridview.</p>
  
  <p>So if a header checkbox is selected all the item templates checkbox should be selected. if any item template checbox is deselcted, the header checkbox should also be deselected.</p>
  
  <p>Thanks</p>