Funcs

It just run a function and doesn't have a return value. How if we want to have a return value? We use Func method.

Func<T, TResult>
Func<T, T1, T2, TResult>

using System;

namespace FunctionalProgramming
{
    class Program
    {      
        static void Main(string[] args)
        {
            Action<string> sayGreeting;

            Func<string, string> conversate = delegate (string message)
            {
                Console.WriteLine(message);
                return Console.ReadLine();
            };

            string input = conversate("What's your name?");
        }
    }
}

So, our inputvariable contains the return value which is whatever you type on console.

Let's make it a full conversation.

using System;

namespace FunctionalProgramming
{
    class Program
    {      
        static void Main(string[] args)
        {
            Action<string> sayGreeting;

            Func<string, string> conversate = delegate (string message)
            {
                Console.WriteLine(message);
                return Console.ReadLine();
            };

            string input = conversate("What's your name?");

            sayGreeting = delegate (string greeting)
            {
                Console.WriteLine(string.Format(greeting, input);
            };

            sayGreeting("Hello, {0}");
            sayGreeting("Bye, {0}");
        }
    }
}