http://www.myelin.co.nz/notes/callbacks/cs-delegates.html
http://msdn.microsoft.com/en-us/library/Bb985784
http://msdn.microsoft.com/en-us/magazine/cc301810.aspx
If you're used to function pointers in C, a delegate is basically a pair of pointers rolled into one:
- A pointer to an object (optional)
- A pointer to a method of that object
You define them like this in C#:
public delegate void FooCallbackType( int a, int b, int c );When you want to use them, you make delegate out of the function you want to call:
class CMyClass
{
public void FunctionToCall( int a, int b, int c )
{
// This is the callback
}
public static void Foo()
{
FooCallbackType myDelegate = new FooCallbackType(
this.FunctionToCall );
// Now you can pass that to the function
// that needs to call you back.
}
}If you want to make a delegate to point to a static method, it just looks the same:class CMyClassWithStaticCallback
{
public static void StaticFunctionToCall( int a, int b, int c )
{
// This is the callback
}
public static void Foo()
{
FooCallbackType myDelegate = new FooCallbackType(
CMyClass.StaticFunctionToCall );
}
}All in all, they do the same thing as interface-based callbacks in C++, but cause a bit less trouble because you don't need to worry about naming your functions or making helper objects, and you can make delegates out of any method. They're more flexible.
