Graphics.IntersectClip Method (RectangleF)
Assembly: System.Drawing (in System.Drawing.dll)
Creates a rectangle with upper-left corner at (0, 0) and sets the clipping region to this rectangle.
Creates a second rectangle with upper-left corner at (100, 100) and sets the clipping region to the intersection of this rectangle and the current clipping region (the first rectangle).
Fills a large rectangle that includes both previous rectangles with a solid blue brush.
Resets the clipping region to infinite.
Draws rectangles around the two clipping regions. It uses a black pen for the first clipping rectangle and a red pen for the second clipping region.
The result is that only the intersection of the two rectangles is filled with blue.