c# - Generic Method assigned to Delegate

Question

I've been a little puzzled with Delegates and Generic Methods.

Is it possible to assign a delegate to a method with a generic type parameter?

I.E:

//This doesn't allow me to pass a generic parameter with the delegate.
public delegate void GenericDelegate<T>() 

someDelegate = GenericMethod;
public void GenericMethod<T>() where T : ISomeClass
{

}

I'm trying to pass this delegate into the function with a generic type of the interface that the method is expecting, with a function like this:

void CheckDelegate(GenericDelegate<ISomeClass> mechanism);

so that I can use the delegate like so:

someDelegate<ImplementsSomeClass>();

Answer 1

Your question makes no sense because you can't ever use an open generic type to declare a storage location (like a local variable or field). It must always be closed.

I understand you want to pass a GenericDelegate<T> to a method taking such a value as an argument. But even then the delegate type becomes closed with T as the generic type parameter.

In your sample code you write

someDelegate = GenericMethod;

but what type is someDelegate supposed to have? It must either be obviously closed (GenericDelegate<string>) or closed with a generic type parameter from the outer scope:

void SomeOuterMethod<T>() where T : ISomeClass {
    GenericDelegate<T> someDelegate = GenericMethod<T>;
}

I hope I understood your problem. If not, please clarify. If you elaborate a little on what you want to accomplish I'll try to suggest a practical solution.

Other languages like Haskell do have support for passing around values of open generic types (in other words, you can have a variable of type IEnumerable<>). This is required to implement monads. The CLR does not have that feature.

---

New thought: instead of a delegate you could create a non-generic base type with a generic method that can be overridden:

interface CheckHandler {
 public void Check<T>(T someArg);
}

Hope that covers your scenario. You can not freely pass any CheckHandler around. Its Check method can then be called with an arbitrary type argument.