using System;

class Program
{
    // M wants to get an instance via Func
    static void M(Func<string> factory)
    {
        Console.WriteLine(factory());
    }

    static void Main()
    {
        // Caller wants to pass just a single instance to M
        string s = Console.ReadLine();

        // By using a lambda () => s
        // this cause a heap allocation for an anonymous class
        M(() => s);

        // On the other hand, by using curried delegate
        // no anonymous class
        M(s.Identity);
    }
}

static class TrickyExtension
{
    // Returns the parameter as-is
    public static T Identity<T>(this T x) => x;
}