Question

I have an html checkbox that controls a list of checkboxes. I want this checkbox to display in a sorta “null” state where it is neither true nor false. Is this possible?

<HeaderTemplate>
   <div style="width:90px">
      Toggle:
      <input id="chkAll"  
      onclick="javascript:SelectAllCheckboxes(this);" 
      runat="server" type="checkbox" />
   </div>
</HeaderTemplate>

Answer 1

No, a checkbox won’t allow a custom third state. You need to find another way to handle it. A few come to my mind:

• Use a dropdown list with three values, or three radio buttons
• Use two checkboxes, one for assigned/null, second for checked/unchecked
• Use an image and javascript to fill a hidden numeric field (it could be a fake checkbox, but it will not match each browser’s look and feel and could look weird)