Show and Hide ModalPopupExtender from JavaScript

Assign a BehaviourID to the ModalPopupExtender using the BehaviourID attribute.

BehaviorID ="ModalBehaviour1"

Use the $find method to get a handle to the Modal Popup Behaviour .

$find ("ModalBehaviour1").

Call your hide and show methods on the acquired handle.

The Javascript would look like this.

<script language="javascript">

    function ShowModalPopup()
 {
     $find("ModalBehaviour1").show();
 }
 function HideModalPopup()
 {
     $find("ModalBehaviour1").hide();
 }

</script >