private void AddComment(object sender, RoutedEventArgs e)
{
double x, y;
string textmsg = "Add a Comment here";
x = 2000;
y = 2000;
Callouts c = new Callouts();
c.type = "Comment";
c.xpos = x;
c.ypos = y;
c.calloutText = textmsg;
c.Render(PadParent);
}