In my program I take appropriate values from the user and then click a button to draw a circle on the same dialog box. However if I change the values and then again click the button to draw, my previous circle is erased and the new one is drawn. What I want is for the previous circles to stay there and not be erased every time a new circle is drawn. I guess it has something to do with how I use Invalidate() statement but Im not sure how to achieve this.

Hi There,
The Problem is When You call Invalidate(); It refreshes the screen so there is only on basestation left on the screen for which you call the function.To show them all make a static counter in base station class and in paint function do this:
for(int i=0;i<=BaseStattionCount;i++)
{
obj.Ellipse (); //for every base station call the function
}
Hope it will work.