Associating data with an event
I just solved the following problem - best explained by concrete example:
WPF Animation.Completed is an event. I need to register this event and when it fires, access custom data associated with the event:
void animate(Graph graph)
{
PointAnimation anim = new PointAnimation();
anim.Completed += new EventHandler(anim_Completed);
// in anim_Completed, I want to call graph.Fix() - how?
}
void anim_Completed(object sender, EventArgs e)
{
// how do I access 'graph' here?
}
Seems like a tough problem. Remembering 'graph' in eg. static variable is not an option, especially if we have more graphs animated at the same time.
Fortunately, C#'s lambdas come to the rescue:
void animate(Graph graph)
{
PointAnimation anim = new PointAnimation();
anim.Completed += new EventHandler((s, e) => { graph.Fix(); });
}
This works because anonymous methods bind to outer variables.
Posted by Martin Konicek
on 2:55 PM
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