使用带有泛型参数的方法作为回调

Question

Let's look at this situation:

private Func<int, int> callback;
public SomeClass(Func<int, int> callback)
{
    this.callback = callback;
}

Then later we can call that function with

callback(5);

and it would return a number.

Now, what I want is something like the following

private Func<T1, T2> callback;
public SomeClass(Func<T1, T2> callback)
{
    this.callback = callback;
}

That delegate would accept a function with a signature like

public T1 SomeFunc<T1, T2>(T2)

and could be called by

callback<int, string>("hello")

which would return an int.

Can this be done in C#?

Answer 1

Sure, but you'll need to make the class generic as well.

Class SomeClass<T1, T2>
{
    private Func<T1, T2> callback;
    public SomeClass(Func<T1, T2> callback)
    {
        this.callback = callback;
    }
 }

Answer 2

If you're storing the callback locally, the easiest thing would be to make the class generic:

public class SomeClass<TParam, TReturn>
{
    private Func<TParam, TReturn> _callback;

    public class SomeClass(Func<TParam, TReturn> callback)
    {
        _callback = callback;
    }
}

Answer 3

Using properties you will have to make the class generic like the other posters said.

It looks a little weird, but if you don't want your class to be generic then you could use generic methods to get and set the callback function, but the downside is that you will have to devise some way to keeping track of the types since you will need to pass them in to call call back. Not sure how useful this would actually be.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1
{

    public class CallbackTest
    {
        public CallbackTest(){}

        private object _CallBack = null;

        public Func<T1, T2> GetCallBack<T1,T2>()
        {            
                return (Func<T1, T2>)_CallBack;
        }

        public void SetCallBack<T1, T2>(Func<T1, T2> value)
        {
            _CallBack = value;
        }



    }
    class Program
    {
        static void Main(string[] args)
        {

            CallbackTest t = new CallbackTest();
            t.SetCallBack(new Func<int, int>(x => x * x));

            Console.WriteLine(t.GetCallBack<int, int>()(10));

            t.SetCallBack(new Func<string, string>(x => x.ToUpper()));

            Console.WriteLine(t.GetCallBack<string, string>()("test"));

            Console.ReadLine();


        }
    }
}