Pass generic method as parameter to another method

Question

This has been asked before (I think), but looking through the previous answers I still haven't been able to figure out what I need.

Lets say I have a private method like:

private void GenericMethod<T, U>(T obj, U parm1)

Which I can use like so:

GenericMethod("test", 1);
GenericMethod(42, "hello world!");
GenericMethod(1.2345, "etc.");

How can I then pass my GenericMethod to another method so that I can then call it in that method in a similar way? e.g.:

AnotherMethod("something", GenericMethod);

...

public void AnotherMethod(string parm1, Action<what goes here?> method)
{
    method("test", 1);
    method(42, "hello world!");
    method(1.2345, "etc.");
}

I just can't get my head around this! What do I need to specify as the generic parameters to Action in AnotherMethod?!

Welladvised

Answer 1

You need to pass into AnotherMethod not a single delegate of some specific type, but a thing which contructs delegates. I think this can only be done using reflection or dynamic types:

void Run ()
{
    AnotherMethod("something", (t, u) => GenericMethod(t, u));
}

void GenericMethod<T, U> (T obj, U parm1)
{
    Console.WriteLine("{0}, {1}", typeof(T).Name, typeof(U).Name);
}

void AnotherMethod(string parm1, Action<dynamic, dynamic> method)
{
    method("test", 1);
    method(42, "hello world!");
    method(1.2345, "etc.");
}

Note that (t, u) => GenericMethod(t, u) cannot be replaced with just GenericMethod.

Interrogative

That's what I was starting to assume. Damn, but thanks! – Welladvised

Answer 2

Consider using an intermediate class (or implement an interface):

class GenericMethodHolder {
    public void GenericMethod<T, U>(T obj, U parm1) {...};
}

public void AnotherMethod(string parm1, GenericMethodHolder holder)
{
    holder.GenericMethod("test", 1);
    holder.GenericMethod(42, "hello world!");
    holder.GenericMethod(1.2345, "etc.");
}

Convalescence

Answer 3

Just wanted to post another solution that I found usefull for a while, especially with caching. When I do a Get from Cache, and the cache item doesnt exist, I call the provided function to get the data, cache it and return. But, this can be used in your specific way too.

Your other method would need a signature similar to this, where getItemCallback is the GenericMethod() you want to be executed. Example has been cleared down for brevity.

public static T AnotherMethod<T>(string key, Func<T> _genericMethod ) where T : class
{
    result = _genericMethod(); //looks like default constructor but the passed in params are in tact.
    //... do some work here 
    return otherData as T;
}

Then you would call your AnotherMethod() as follows

var result = (Model)AnotherMethod("some string",() => GenericMethod(param1,param2));

I know its about several months later but maybe it will help the next person, as I forgot how to do this and couldn't find any similar answer on SO.

Threap