OnClientDragStart

The OnClientDragStart client-side event occurs each time the user begins to drag an item. This event can be cancelled.

The event handler receives two parameters:

1. The instance of the listbox firing the event

2. An event arguments parameter containing the following methods:

• get_sourceItem() - returns the first selected item that is dragged

• get_sourceItems() -returns an array of the selected items that are dragged

• set_cancel() - lets you cancel the event and prevent the dragging.

• get_domEvent() - returns the DOM event object

• get_htmlElement() - returns the DOM html element which the item is dropped onto.

The following example shows how to cancel the event if the number of the selected/dragged items is greater than 3:

function onClientDragStartHandler(sender, e) {
    if (e.get_sourceItems().length > 3) {
        e.set_cancel(true);
    }
}