C# Delegates

Christopher · November 19th, 2009, 03:11 PM

Please can someone provide me with a short explanation of what a delegate is, and what it would be used for?

Why would we use delegates over a function?

Thank you

samjudson · November 19th, 2009, 03:14 PM

A delegate is a reference to a function, so you can call a delegate as if it were a function and it will call the function it points to.

Have you tried googling "C# delegate"?

You use them all the time but might not be aware of it - events in the .Net framework use delegates.

Christopher · November 19th, 2009, 03:17 PM

Thanks Sam

I have just now Googled C# Delegates, but the explanation is as vague as the explanation in Wrox Beginning Visual C#.

Why would i make a reference to a function via a delegate, why dont i just call the function directly?

samjudson · November 19th, 2009, 03:21 PM

Because the function might not exist, or have been written when you write you code to call it, you have a 'property' which you declare as a delegate - someone else can set this property to point to their own function (e.g. an event handler) and when you call the delegate it calls their function.

If you only ever want to call one function and you are writing both the code to be called and the calling code at the same time then you wouldn't need delegates.

Christopher · November 19th, 2009, 03:32 PM

dude, thank you!! You're making this a whole lot simplier for me!

Uhm, could you set a property of an object to point to a function using a delegate. IE: could i add a button to a form, and using events assign a specific delgate to an onclick event, without having to add code?

samjudson · November 19th, 2009, 05:16 PM

I don't understand what you mean by 'without adding code'.

Button1.OnClick += new MouseClickHandler(Button1_OnClick);

In the above example the OnClick event is a delegate property of the Button class. It takes a delegate of type MouseClickHandler, which can point to any method which matches the MouseClickHandler delegate signature i.e. void F(object, MouseEventArgs)

Bob Bedell · November 19th, 2009, 06:18 PM

0000000000

Christopher · November 20th, 2009, 05:08 AM

Hi Sam, Bob

Thank you both for your explanations - they're invaluable. To be honest, I am a new developer. I studied IT at uni, with a bit of Delphi, but in the last 5 years of work history, I have not touched on any development. I then wanted to get back into it, and decided C# is the best avenue for this... And my boss is getting me involved in transferring our current office application into WPF. I hope to also get involved in developing ASP apps (correct terminology??) and potentially BizTalk and XML/XAML.

Baby steps first.

I hope to receive further explanations from you with my future questions.

Thank you!!

Chris

PS I am relatively new to this Forum biz, but can i setup an RSS feed to this forum, even though i get immediate updates via email, i'd liked to get a grasp of RSS feeds