How to break a program before called to Main()?

Question

This question ask in interview... please tell me...

Sanjeeb Lenka · Answer

hi, try this console program and check: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading; namespace IfExample { class braekcs { static braekcs() { Console.WriteLine("Test123"); Thread.Sleep(5000);//it will pause the program for 5 sec Environment.Exit(1); //after that it kills the process and main will not execute } static void Main(string[] args) { Console.WriteLine("Test111"); Console.ReadLine(); } } }

Maha · Answer

Thank you for your explanation.

Sanjeeb Lenka · Answer

Thanks Vulpes for the detail explanation .

Vulpes · Answer

If a class has a static constructor, then it will run once - and once only - before any other static members are referenced or an instance constructor of that class is called. This applies even if the class concerned is the one which contains the Main() method. So, in Sanjeeb's example, breakcs's static constructor will run before the Main() method is called by the system. You should therefore be able to step through the code in VS until the following line is reached: Environment.Exit(1); This will cause the current process to be killed stone dead and so the Main() method will never be called :) Incidentally, this forum seems to have suddenly lost the ability to edit one's posts - the Edit button has disappeared! I said in my previous post that calling 'return' from the static constructor would prevent the Main() method from being called. That, of course, is wrong - only Environment.Exit(1) or something similar such as System.Diagnostics.Process.GetCurrentProcess().Kill() will do that. EDIT: The Edit button's back now!

Maha · Answer

Usually Main() method is the entry point and if you use Step Into key(F11) you can see the step by step execution of the programme and F5 key start debugging. Programme produced by Sanjeeb Lenka seems violating usual norms. Whether you use F11 or F5 key programme is executing and producing console output and you can't see the step by step execution of the programme. Please explain the reason.

Vulpes · Answer

Actually, I've just thought of a way to do it! If you include a static constructor in the same class as the Main() method and call 'return' (or one of the other options in my first post) from the static constructor that will prevent the Main method from running at all.

Vulpes · Answer

To the best of my knowledge, there's no way in which you can prevent the Main() method in a .NET exe from running at all. However, you can prevent it from running to completion by either calling 'return' (or 'return 1' if you're using the version of Main() which returns an int) or by calling Environment.Exit(1) which kills the process.

How to break a program before called to Main()?

Answers (7)