using System;

using System.Threading;

using System.Threading.Tasks;

class DelegateTest<T>

{

    public DelegateTest()

    {

        if (typeof(T) == typeof(int))

        {

            _doSomething = (Action<T>)(object)DoSomethingInt;

        }

    }

​

    Action<T> _doSomething;

​

    public void InvokeDoSomething(T x) => _doSomething(x);

​

    static void DoSomethingInt(int val)

    {

        Console.WriteLine("Hello world! The argument was {0}", val);

    }

}

​

delegate void DoSomethingDelegate<T>(T val);

​

public class Program

{

    public static async Task Main()

    {

        var o = new DelegateTest<int>();

        o.InvokeDoSomething(1);

    }

}