What is the accepted pattern for an application that can be run as a service or as a console application

Question

I have a project that is deployed to production as a windows service. However for local development purposes it would be useful to run it as a console application. At the moment

Answer 1

My advise? Put all your logic for your service in a separate assembly. (A class library or DLL.) Then create one project as service which references your class library and puts the code to use as services. Create a second console project which also references your class library but which will make it available as a console application. You would end up with three different projects in your solution but it does allow you to keep things separate. Actually, this would make it possible to extend your service in several other shapes too. You could, for example, create a 4th project as a web service and thus call your service from a web browser on a client system. Because the software logic is separated from the usage logic, you gain lots of control over it.

Be aware that a service will possibly run with more limitations than a console application. In general, services don't have network access by default, don't have a monitor assigned to them to display error messages and in general run with a limited user account or system account. Your service might work as a console yet fail as a service because of this.

Answer 2

I have done this before by implementing a normal Windows Service (by deriving from ServiceBase), but putting a check in the main method to check for a command line argument.

If the args contain /console, start the console version, otherwise start the service.

Something like this:

internal class MyService : ServiceBase
{
    internal static void Main(string[] args)
    {
        if (args.Length == 0)
        {
            // run as a service....
            ServiceBase[] servicesToRun = new ServiceBase[] {new MyService()};
            Run(servicesToRun);
        }
        else
        {
            // run as a console application....
        }
    }
}

Answer 3

I suspect your test project was configured as a windows exe, not a console exe. With a windows exe Console.ReadLine will return immediately.

To have a console exe that works both as a service and at the command line, start it as a service project (in Visual Studio) - and add a check on Environment.UserInteractive - i.e.

static void Main() {
    if(Environment.UserInteractive) {
        // code that starts the listener and waits on ReadLine
    } else {
        // run the service code that the VS template injected
    }
}

You can of course also use a command line switch. I have example on microsoft.public.dotnet.languages.csharp that acts as:

• an installer / uninstaller
• a service
• a console-mode app

depending on the switches

Answer 4

There are already two good answers above - but I thought I'd post a link to Brian Noyes' Debuggable Self-Host Windows Service Project blog post - it talks about WCF but should apply to any 'Windows Service'.

The best thing is the sample code - if you can't figure out where the above examples 'fit', grab the complete project and see how it works. Thanks Brian!