WMI call takes too much time when system Starts/ReStarts

Question

I want to get the path of the Windows Service,

var managementObjectSearcher = new ManagementObjectSearcher(\"Select * from Win32_Service where serviceName = MySe         


        

Answer 1

Since you're retrieving the service by Name, which a key property of the Win32_Service class, try retrieving the instance directly instead of searching for it:

string GetMyServicePath()
{
    string path = "Win32_Service.Name=\"MyService\"";

    using (ManagementObject service = new ManagementObject(path))
        return (string) service.GetPropertyValue("PathName");
}

Here's a quick benchmark I threw together to compare direct retrieval vs. searching:

private const int LoopIterations = 1000;

private const string ServiceClass = "Win32_Service";
private const string ServiceName = "MyService";
private const string ServiceProperty = "PathName";

private static readonly string ServicePath = string.Format("{0}.Name=\"{1}\"", ServiceClass, ServiceName);
private static readonly string ServiceQuery = string.Format(
    "SELECT {0} FROM {1} Where Name=\"{2}\"",
    ServiceProperty, ServiceClass, ServiceName
);
private static ManagementObjectSearcher ServiceSearcher = new ManagementObjectSearcher(ServiceQuery);

static void Main(string[] args)
{
    var watch = new Stopwatch();

    watch.Start();
    for (int i = 0; i < LoopIterations; i++)
    {
        var servicePath = GetServicePathByKey();
    }
    watch.Stop();
    Console.WriteLine(
        "{0:N0} iterations of GetServicePathByKey() took {1:N0} milliseconds",
        LoopIterations, watch.ElapsedMilliseconds
    );

    watch.Restart();
    for (int i = 0; i < LoopIterations; i++)
    {
        var servicePath = GetServicePathFromExistingSearcher();
    }
    watch.Stop();
    Console.WriteLine(
        "{0:N0} iterations of GetServicePathFromExistingSearcher() took {1:N0} milliseconds",
        LoopIterations, watch.ElapsedMilliseconds
    );

    watch.Restart();
    for (int i = 0; i < LoopIterations; i++)
    {
        var servicePath = GetServicePathFromNewSearcher();
    }
    watch.Stop();
    Console.WriteLine(
        "{0:N0} iterations of GetServicePathFromNewSearcher() took {1:N0} milliseconds",
        LoopIterations, watch.ElapsedMilliseconds
    );
}

static string GetServicePathByKey()
{
    using (var service = new ManagementObject(ServicePath))
        return (string) service.GetPropertyValue(ServiceProperty);
}

static string GetServicePathFromExistingSearcher()
{
    using (var results = ServiceSearcher.Get())
    using (var enumerator = results.GetEnumerator())
    {
        if (!enumerator.MoveNext())
            throw new Exception();

        return (string) enumerator.Current.GetPropertyValue(ServiceProperty);
    }
}

static string GetServicePathFromNewSearcher()
{
    using (var searcher = new ManagementObjectSearcher(ServiceQuery))
    using (var results = searcher.Get())
    using (var enumerator = results.GetEnumerator())
    {
        if (!enumerator.MoveNext())
            throw new Exception();

        return (string) enumerator.Current.GetPropertyValue(ServiceProperty);
    }
}

Enumerating the searcher results directly is about as fast as I could make it, marginally faster than using a foreach block and twice as fast as using LINQ. On my 64-bit Windows 7 Professional system with the ServiceName constant set to Power I got these results:

1,000 iterations of GetServicePathByKey() took 8,263 milliseconds
1,000 iterations of GetServicePathFromExistingSearcher() took 64,265 milliseconds
1,000 iterations of GetServicePathFromNewSearcher() took 64,875 milliseconds