caching GDI+ objects?

[CWinThread]

In the C# books I've read, drawing objects such as pens, brushes, etc are usually created in a using declaration in OnPaint(). I don't see anything wrong with this as it seems to be more resource friendly but I've heard others say these objects should be cached, such as storing them as instance fields. Are there any guidelines for going one way versus the other?

[Dave Kreskowiak]

The only guidelines I can suggest are: 1) How many times a second are you going to repaint your form? If your writting an analog clock that repaints itself every 50 milliseconds, you'll want to create your pens and brushes once and cache them so you're not creating and destroying them a couple hundreds times per second. If you only repaint the form when Windows tell you to, then you could probably get away with creating and destorying your pens and stuff on demand. 2) If you're painting alot of static stuff. In the clock example, the clock face and hands don't change between any repaints. Just the positions of certain items change. In this case you could get away with caching your drawing objects. If you're painting dynamic data that frequently changes the colors of what your drawing between repaints, then you'll have to create and destroy your drawing objects on demand. RageInTheMachine9532 "...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome

[CWinThread]

Thanks Dave, Those are some good examples of when caching might be useful.