C# - Restoring GDI+ after alt tab

[RobAMacAF]

I am using GDI and I am having some issues. When I alt-tab out of the window and go back to it the drawing events don't fire. Which should I be using to do this? You might not be able to understand the cod ebut I am code like this to draw...

g.DrawString(noDef, fnt, new SolidBrush(Color.Black), rect, sf);
g.FillRectangle( new SolidBrush(Color.Green), rect);

Any help would be great, Thanks
Rob