c# : console application - static methods

Question

why in C#, console application, in "program" class , which is default, all methods have to be static along with

static void Main(string[] args)

Answer 1

Member functions don't have to be static; but if they are not static, that requires you to instantiate a Program object in order to call a member method.

With static methods:

public class Program
{
    public static void Main()
    {
        System.Console.WriteLine(Program.Foo());
    }

    public static string Foo()
    {
        return "Foo";
    }
}

Without static methods (in other words, requiring you to instantiate Program):

public class Program
{
    public static void Main()
    {
        System.Console.WriteLine(new Program().Foo());
    }

    public string Foo() // notice this is NOT static anymore
    {
        return "Foo";
    }
}

Main must be static because otherwise you'd have to tell the compiler how to instantiate the Program class, which may or may not be a trivial task.