Stopping onclick from firing when onclientclick is false?

Is it possible to use the onclientclick property of a button to do a clientside check. If the check returns true, then fire the onclick event. If the clientside check returns false, don't fire the onclick event.

Is that possible?

UPDATE:

These 2 work:

Stops the form from submitting:
OnClientClick="return false;"

Allows the form to submit:
OnClientClick="return true;"

The next 2 do not work:

// in js script tag
function mycheck() {
    return false;
}

// in asp:button tag
OnClientClick="return mycheck();"

// in js script tag
function mycheck() {
    return true;
}

// in asp:button tag
OnClientClick="return mycheck();"

It submits the form both times.

Why is that?

You want to add return inside OnClientClick after a function is called. Otherwise, the button will post back even if function returns false.

<asp:button ID="Button1" runat="server" OnClick="Button1_Click" 
    OnClientClick="return checkValidation()" Text="Submit" />

<script type="text/javascript">
    function checkValidation() {
        return confirm('Everything ok?');
    }
</script>

Sure. If you use return false within your OnClientClick it will prevent any navigation from happening. So you're code would look like:

<asp:LinkButton runat="server" OnClientClick="if(!ValidatePage()) { return false;}" />

Yes you can, In onclientClick function call use preventDefault()

function onclientClickFun(e)
{
  if(!IsValidationSuccess)
 {
   e.preventDefault();
 }

}

OR

function onclientClickFun(e)
{
  if(!IsValidationSuccess)
 {
   return false;
 }

}