Generic Delegate

Question

I want to have a delegate for a method which takes one parameter and returns a result, both of the same type. I also want the type to be determined by a generic type argument but the following syntax fails me.

delegate T SomeDelegate(T param)<T>;

How could I achieve this?

Answer 1

You have to put<T> between the Delegate-Name and the open bracket: delegate T SomeDelegate<T>(T param);. After the close-bracket you can only say, which type T must be, to be sure the correct types are passed. For example:

delegate T SomeDelegate<T>(T param) where T : IDisposable;

Often this is necessary, to be sure that T is inherited by Disposable. So you later can cast T as IDposposable and call some method of the interface.

Notice, only interfaces can be user for filtering.

Answer 2

The type parameter must be declared between the method/delegate name and the regular parameter list:

delegate T SomeDelegate<T>(T param);