如何在 NetCore 应用程序中使用 Microsoft.Management.Infrastructure 订阅事件？

Question

I'd like to know how to subscribe and receive events in a NetCore application using the library Microsoft.Management.Infrastructure.

So far I'm able to query some data using something like this:

var options = new CimSessionOptions();
var securePassword = new SecureString();
foreach (var c in password)
    securePassword.AppendChar(c);

var credentials = new CimCredential(PasswordAuthenticationMechanism.Default, "", "user", securePassword);
options.AddDestinationCredentials(GetCredentials(user, password));

CimSession session = CimSession.Create(url, options);
var queryInstance = mySession.QueryInstances("a namespace", "WQL", "a query");
foreach (var instance in queryInstance)
    Console.WriteLine(instance.ToString());

Searching on Internet, I saw examples doing this using System.Management, like the following one:

ManagementEventWatcher watcher = new ManagementEventWatcher("namespace", "query");
watcher.EventArrived += new EventArrivedEventHandler(EventArrived);
watcher.Start();

But unfortunately I can't use this package, I just need the equivalent but using MMI.

I've seen some class that maybe could help me in this task like CimIndicationWatcher which is part of the Microsoft.Management.Infrastructure.CimCmdlets package, however I imported it to my project but I can't access any of the classes in it.

There's a lack of documentation/examples about the use of this class or this scenario in general.

Answer 1

I found a way, not sure if the correct one, but I'm able to receive events using Microsoft.Management.Infrastructure library.

This is how I did it:

/// Create an observer class
class CimInstanceWatcher : IObserver<CimSubscriptionResult>
{
    public void OnCompleted()
    {
        Console.WriteLine("Done");
    }

    public void OnError(Exception e)
    {
        Console.WriteLine("Error: " + e.Message);
    }

    public void OnNext(CimSubscriptionResult value)
    {
        Console.WriteLine("Event received: " + e.Message);
    }
}

Now, use it in this way:

static void Main(string[] args)
{
    CimSession session = CimSession.Create("MY-PC");
    // create a watcher
    var watcher= new CimInstanceWatcher();
    var queryInstance = GetValues(session).Subscribe(watcher);

    // close application once events are no longer required to be received
    Console.ReadLine();
    session.Close();
}

public static CimAsyncMultipleResults<CimSubscriptionResult> GetValues(CimSession _session)
{
    // Subscribe to any event, in this case, fire an event when an application is opened
    return _session.SubscribeAsync(@"root\cimv2", "WQL", "SELECT targetInstance.Name FROM __InstanceCreationEvent within 2 " +
        "WHERE targetinstance isa \"Win32_Process\"");
}

Now events will be registered on the OnNext method, if there's an error it will also be prompted to the observer.