Draw event has 0,0 for Area coordinates

Question

I am trying to draw in a DrawingArea in GTK 2.12 in Mono with C#. However, when I call QueueDrawArea() and send in the current point the point values are not present in the DrawingArea's Expose Event.

The idea is that a rectangle will be drawn where I drop something in this area, but I don't want to redraw the whole area.

    drawarea.DragDrop += new DragDropHandler (delegate(object o, DragDropArgs args) {
        Console.WriteLine(args.X + ", " + args.Y);  //correct drop coords shown here
        drawarea.QueueDrawArea(args.X, args.Y, 10, 10);
    });

ExposeEvent for drawarea:

protected override bool OnExposeEvent(Gdk.EventExpose args)
        {
            Console.WriteLine (args.Area.X + ", " + args.Area.Y);  //(0, 0)
            context = Gdk.CairoHelper.Create(args.Window);
            context.SetSource(mainSurface);

            Cairo.Color color = new Cairo.Color(0.4, 0.8, 0, 1);
            context.Antialias = Antialias.None;
            context.SetSourceRGBA(color.R, color.G, color.B, color.A);
            context.LineCap = LineCap.Round;

            context.Rectangle(args.Area.X, args.Area.Y,  50, 50);
            context.LineWidth = 10;
            context.Clip();
            context.Paint();
            return true;
        }

I have been unable to find why this is happening or what potential link I'm missing between calling QueueDrawArea() and the Draw event firing with the dirty region's values.