c# - Check if a service exists on a particular machine without using exception handling

Question

Don't know if there is a better way to do this, so that is the reason for the question. I can check if a service exists on a particular machine with the following code:

bool DoesServiceExist(string serviceName, string machineName)
{
    ServiceController controller = null;
    try
    {
        controller = new ServiceController(serviceName, machineName);
        controller.Status;
        return true;
    }
    catch(InvalidOperationException)
    {
        return false;
    }
    finally
    {
         if (controller != null)
         {
             controller.Dispose();
         }
    }
}

but this seems like an ineffecient solution to me (due to the exception handling). Is there a better way to check if a service exists. Note - I have recently switched to .Net 4.0 so if someone knows of a better solution in 4.0 that would be acceptable.

EDIT: Here is a sample c# console app to test the performance of my example as well as the GetServices code sample. In my testing I found that the GetServices is much more performative in the case where the service does not exist, but is twice as slow when the service does exist:

    static void Main(string[] args)
    {
        string serviceName = string.Empty;
        string machineName = string.Empty;

        var sw = new Stopwatch();
        sw.Reset();
        sw.Start();
        for (int i = 0; i < 1000; i++)
        {
            ServiceExistsException(serviceName, machineName);
        }
        sw.Stop();
        Console.WriteLine("Elapsed time: " + sw.ElapsedMilliseconds.ToString());
        sw.Reset();
        sw.Start();
        for (int i = 0; i < 1000; i++)
        {
            ServiceExistsGetList(serviceName, machineName);
        }
        sw.Stop();
        Console.WriteLine("Elapsed time: " + sw.ElapsedMilliseconds.ToString());

        Console.WriteLine("Done");
        Console.ReadLine();
    }

    static bool ServiceExistsException(string serviceName, string machineName)
    {
        ServiceController controller = null;
        try
        {
            controller = new ServiceController(serviceName, machineName);
            string name = controller.DisplayName;
            return true;
        }
        catch (InvalidOperationException)
        {
            return false;
        }
        finally
        {
            if (controller != null)
            {
                controller.Dispose();
            }
        }
    }

    static bool ServiceExistsGetList(string serviceName, string machineName)
    {
        ServiceController[] services = null;
        try
        {
            services = ServiceController.GetServices(machineName);
            var service = services.FirstOrDefault(s => s.ServiceName == serviceName);
            return service != null;
        }
        finally
        {
            if (services != null)
            {
                foreach (ServiceController controller in services)
                {
                    controller.Dispose();
                }
            }
        }
    }
}

Answer 1

You can use the ServiceController.GetServices() method to get all of the services on the machine, then look through them to see if one exists named what you are looking for:

bool DoesServiceExist(string serviceName, string machineName)
{
    ServiceController[] services = ServiceController.GetServices(machineName);
    var service = services.FirstOrDefault(s => s.ServiceName == serviceName);
    return service != null;
}

The FirstOrDefault() extension method (from System.Linq) will return either the first service with the given name, or a null if there is no match.

---

To address your speed issue:

The difference between the two approaches for a single method call is negligible, regardless of whether the service is found or not. It will only be a problem if you are calling this method thousands of times—in which case get the list of services once and remember it.