GDI+ FAQ: Disposing of GDI+ resources
You will often see the following in C# or VB
code...
myGraphicsObject.DrawLine(new
Pen(Color.Black,1), 0, 0, 10, 10)
The Pen object in this case is created inline and
never disposed of. In old-style GDI, this was a recipe for disaster
because the resources associated with GDI pens and brushes were finite and
could leak, causing the system to eventually freeze up.
GDI+ is still an unmanaged technology but .NET
provides us with managed wrappers that are lifetime managed by the Garbage
Collector. This means that when the pen object goes out of scope, it will
be marked for garbage collection and eventually reclaimed by the system,
freeing up its resources as it goes.
This kind of technique is fine for quick demos and
so on but if you're serious about your graphics you should behave nicely
and preemptively dispose of GDI+ objects when you're done with
them.
Explicitly disposing of an object frees its
unmanaged resources and allows them to be recycled more quickly and
efficiently.
The proper usage is to create, use and dispose of an
item. in the right place. For example...
void
override OnPaint(PaintEventArgs e)
{
Pen p=new
Pen(Color.Black,1);
e.Graphics.DrawLine(p,0,0,10,10);
p.Dispose();
}
If your application uses a lot of pens or
brushes you can manage them by assigning them when the application first
runs and disposing of them when the application closes during the Dispose
method.
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