Debugging Windows Services in Visual Studio

26. September 2009 04:22 by Matt Wrock in   //  Tags:   //   Comments

One challenge involved in developing windows service applications is debugging them in Visual Studio. I don't know why Visual Studio does not provide better support for this, but I've seen some creative techniques employed to make debugging windows services possible. One popular method is to put a really long thread.sleep(30000) in the OnStart event and then install the service, start it and attach the debugger to the service's process hoping that it will take less than 30 seconds to start it, find the process and attach.

There is a better way and it is quite trivial.

There is one prerequisite: Make sure you do not have service logic in your OnStart() method. This turns out to be a good thing either way. I've seen 100 line service OnStart methods that put a good deal if not all of the logic into this one method. Well what if you want to reuse this logic in a console, WPF or win forms app? Its not a very flexible methodology. I believe that a windows service project should never contain more than your installer and entry point class and the entry point class only handles start, stop and pause by caling into a completely separate assembly. However, before over philosophizing this, lets quickly jump into how to setup your service project so that it can be easily dubugged in VS.

Follow these steps:

  1. Change your Main() entry point method to Main(string[] args)
  2. Change the Output Type property of the servce project from Windows Aplication to Console Application
  3. Your Main(string[] args) method shouldlook something like:
        static void Main(string[] args)
        {
            if (args.Length > 0)
            {
                MyApp app = new MyApp();
                app.Run();
            }
            else
            {
                ServiceBase[] ServicesToRun;
                ServicesToRun = new ServiceBase[]
                {
                    new Service1()
                };
                ServiceBase.Run(ServicesToRun);
            }
        }

Finaly, in the Debug section of the project properties, provide a command line argument.

Your OnStart() should contain the same app startup code as you Main method:

        protected override void OnStart(string[] args)
        {
            MyApp app = new MyApp();
            app.Run();
        }

Thats it. Now hit F5 and you will see a command window pop up and all of your break points should be recognized. MyApp contains the meat of te logic. Main and OnStart are just dumb harnesses.

 

 

blog comments powered by Disqus

About Me

Hey thats me!

I'm Matt Wrock with over thirteen years of experience architecting scalable, distributed, high traffic web applications. I currently live in Woodinville, WA with my wife, two daughters, three dogs and cat. I work for Microsoft as a Sr. Software Engineer working in Cloud Developer Services. I'm also project founder and owner of http://www.requestreduce.org and a committer to http://chocolatey.org.

Month List