This method is automatically called when the system is running low on memory. Application developers who override this method in order to release resources must call base.DidReceiveMemoryWarning(), as shown in the following code, taken from the “Media Notes” sample:

public override void DidReceiveMemoryWarning ()
{
    photoMap.Clear ();
    View = null;
    photoImageView = null;
    toolbar = null;
    syncIsNeeded = true;
    base.DidReceiveMemoryWarning();
}