See Your Program Twice

Approach #1

With the first approach, your code will look identical to that in the original Hello World program. Instead of making a modification to the code, you simply run it in release mode (without debugging) by pressing Ctrl + F5.

Approach #2

Below is the code for the second approach, which involves adding in Console.ReadKey(); to the end of your code. This forces your program to wait at the end until you press a key.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace HelloWorld
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello World!");
            Console.ReadKey();
        }
    }
}

Combining the Two

If you add in Console.ReadKey(); and run in release mode, you'll have to press a key twice to end the program. This is because your code will include the line that waits for it (from Approach #2) but also, when the program ends, you'll get the normal "Press any key to continue..." statement, which you'll need to press a key for again.

Since both mechanisms are in place, and they're both waiting for a key press, you're going to have to do so twice.