Monad.cs

public static class Program
{
    public static void Main()
    {
        var x = 5.Bind(Add1)
            .Bind(Times2)
            .Bind(Square);
    }

    public static TOutput Bind<TInput, TOutput>(this TInput input, Func<TInput, TOutput> func)
    {
        return func(input);
    }

    public int Add1(int x) => x + 1;

    public int Times2(int x) => x * 2;

    public int Square(int x) => x * x;
}