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Why can't a windows service created in C# detect that a screen saver is currently running?

As part of some work I need to get done for Windows 10, I have written a code in C# that essentially detects every minute whether a PC is in screen saver mode or not, and it writes to a table in MySQL the relevant status ("PC in use" if the screen saver is off, "available PC" if the screen saver is on).
I did this using (full link if required - https://www.codeproject.com/Articles/17067/Controlling-The-Screen-Saver-With-C):
// Returns TRUE if the screen saver is actually running
public static bool GetScreenSaverRunning( )
{
bool isRunning = false;
SystemParametersInfo( SPI_GETSCREENSAVERRUNNING, 0,
ref isRunning, 0 );
return isRunning;
}
The code works flawlessly in console application mode (I made a loop to test it out over a minute with a check up on screen save status every 10 seconds), this means in MySQL the status was set correctly every time, depending on the screen save status at the moment of the check up.
The problem occurs when I use this code for a windows service. The service is installed correctly, the log on tab is set on Local System (I also tried with the logged in user instead, same results) and I allow the service to interact with the desktop, just in case, but the difference here is that no matter if the PC enters screen save or not, it always returns false on GetScreenSaverRunning(), thus setting the status of the PC in MySQL as "PC in use", even if the screen saver is on at the moment of check up.
I get the sense that the problem isn't in the code itself, since it works without any issues as a console application, but perhaps something behind the scenes. I tried to search here and on many other websites, haven't found anything related to such a problem.
Does anyone have any idea at all what might be the issue? Any help and/or suggestions will be greatly appreciated!
Thank you in advance.
(I could post the code if required, but it is pretty much straight forward and the main part of it, controlling the screen save detection, is taken from the website mentioned above, afterwards it's a simple if (GetScreenSaverRunning() == true) )

Ever since Vista, Services are barred from a Interactive Session. Even if they run under the same rights, they do not get a interactive Session. I would guess that is getting in the way here.
While you can overwrite this behavior in the Service settings, this is not adviseable for new code. Consider making this a Background Task started by the Task Sheduler instead.

Because the windows service runs in different session then the windows logon. You can't interact with the desktop related services unless you run the windows service in win logon session. There used to be an option in Windows service manager where you can set the properties to "Interact with desktop session" but I don't think that ever worked.
There's a work around to run the windows service using the win logo session.
See this helper class that can get the current logged on user session and interact with the desktop services. https://github.com/murrayju/CreateProcessAsUser/blob/master/ProcessExtensions/ProcessExtensions.cs

Wait for an launched application to stop

We are currently working on a project in UWP where we have to start an external application to modify some documents.
We looked into the Windows.System.Launcher API but it seems that we need more than what it can offer us.
As we launched the application from a file, we use the LaunchFileAsync method, based on the example given by the MSDN :
async void DefaultLaunch()
{
// Path to the file in the app package to launch
string imageFile = #"images\test.png";
var file = await Windows.ApplicationModel.Package.Current.InstalledLocation.GetFileAsync(imageFile);
if (file != null)
{
// Launch the retrieved file
var success = await Windows.System.Launcher.LaunchFileAsync(file);
if (success)
{
// File launched
}
else
{
// File launch failed
}
}
else
{
// Could not find file
}
}
So far, the example suit us well but we also need to be warned when the user is done with the file. The best would be to be able to give the launcher a callback method.
We haven't found anything like that yet in the documentation. Is this even possible ? Do we need to use another solution ?
TL;DR : Is there a solution to open another application from a UWP app and wait for it to return a result object ?

If the external app is also a UWP app then Launcher.LaunchUriForResultsAsync is designed for this. It will launch the target app then wait for the app to call back with the results.
See Launch an app for results for a full walkthrough of how this works.
If the target app isn't a UWP app then you can implement the same thing yourself: both apps declare a protocol. The client launches the server with the server's protocol. When the server's done it notifies the caller by launching the client's protocol.
You might also want to look into App Services which allow a UWP server app to expose a REST-like service to clients on the local system. 

The app process isolation model means you can't do this from a UWP app. As you just want to know when an arbitrary program has finished you could write this in traditional .net/win32 and include that in your UWP app via the desktop bridge.

Performance considerations when getting license information for WP app

Introduction
I have a Windows Phone 8.1 Silverlight (WP8.1 SL) based app in the store. Some users complain about performance issues when they have a bad network connection. I searched a bit and came up with the idea that it might be related to new LicenseInformation() that gives me the information of whether the app is running in Trial mode or not. The question is, whether this requires network information or not, and whether CurrentApp.LicenseInformation is a suitable replacement for a WP8.1 SL app.
Background and What I did so far
In general, the app does not need a network connection (no data to load, no advertisements, ...). To confirm that I used Fiddler to watch over the network sent by my phone. The result was that no network traffic is generated. However, the problem still persists.
After a lot of research and playing around I got the feeling that this issue might be related to the code part that checks on whether the app is in trial mode or not. I use the following code to check that.
var li = new LicenseInformation();
if (li.IsTrial()) {
...
}
I do this a couple of times during startup. So in case IsTrial() requires a network connection this could be the actual issue when there is only a bad connection available. But again, I couldn't find anything using Fiddler. The documentation (see here) for LicenseInformation does not mention whether a network connection is required or not.
Searching around I found that there is an updated interface available for both WP 8.1 SL and also W10M UWP.
var li = CurrentApp.LicenseInformation;
if (li.IsTrial) {
...
}
Its documentation clearly states that there is no network connection required for that (see here).
Even though the docs say that CurrentApp.LicenseInformation is also available on WP8 I also found some references that say that you only get a reliable answer for the IsTrial-question when using new LicenseInformation() (e.g. here).
Actual Questions
Is new LicenseInformation() required on WP8.1 SL, or can I use CurrentApp.LicenseInformation as well?
Does new LicenseInformation() require a network connection compared to CurrentApp.LicenseInformation?

WebAuthenticationBrowser.AuthenticateAsync() kills the UWP app

I have a universal Windows 10 app where I use
var token = await WebAuthenticationBrowser.AuthenticateAsync(...)
to authenticate user against facebook. It all works fine in a common scenario when it's just the foreground app. However when I add a BackgroundMediaPlayer, start music playback and communication between foreground and background, calling
var token = await WebAuthenticationBrowser.AuthenticateAsync(...)
actually kills my foreground app. When user finishes the authentication in the broker, he is taken back to the app - but it was killed and is re-instantiated. This of course means that awaiting AuthenticateAsync() doesn't produce any results, because it's a new instance of the app.
I would understand this behavior when calling WebAuthenticationBrowser.AuthenticateAndContinue() which was introduced in WP8.1, but this API has been deprecated in UWP.
So my questions are - is this expected behavior (app being killed and relaunched)? If so, how do I get the token from WebAuthenticationBroker during app relaunch?
Here is a sample project to reproduce (with exact steps in a txt file): https://t.co/XtmESd9o5r
Here is a video running the sample (first launch the broker without BackgroundMediaPlayer running, then with it running): http://youtu.be/VcZXBOTiD1Y
I started a conversation about this in twitter: https://twitter.com/lancewmccarthy/status/685152844849262593 but so far the only help I got was to "check the activation kind" with this link: https://msdn.microsoft.com/en-us/library/windows/apps/windows.applicationmodel.activation.activationkind.aspx.
The link describes activationKind has "WebAuthenticationBrokerContinuation", but
1) that's only for Windows Phone, not Windows 10
2) when you run the sample, you will never receive it. Only "Launched", with previousExecutionState "Terminated"

How can I connect to a Server Side USB (HID) Device from within an ASP.NET Application?

I'm trying to write my own controller for a USB device instead of using the SDK that comes with the product (I feel the sdk is sub-par).
The USB Device is plugged into the SAME SERVER that this application is running on.
So I decided to head over to Nuget and grab the HidLibrary
PM> Install-Package hidlibrary
and I proceeded to follow the example found on GitHub.
First I went into my control panel to verify the VendorID and the ProductID
And I dropped it into my code.
Then I set a breakpoint on the line that grabs the device, but unfortunately it always comes back null.
using HidLibrary;
public class MyController : ApiController
{
private const int VendorId = 0x0BC7;
private const int ProductId = 0x0001;
private static HidDevice _device;
// POST api/<controller>
public string Post(CommandModel command)
{
_device = HidDevices.Enumerate(VendorId, ProductId).FirstOrDefault();
if (_device != null)
{
// getting here means the device exists
}
else
{
// ending up here means the device doesn't exist
throw new Exception("device not connected");
}
return null;
}
I'm hoping it's something silly, and not some deal-breaking permissions issue regarding connecting to a USB device directly from an IIS worker.

Despite your hopes to be something silly, it is not. You have some deal-breaking permission issues. If you will browse Mike O'Brien's code from GitHub of the Hid Library you will see that it calls Win32 API functions located in: kernel32.dll, setupapi.dll, user32.dll, hid.dll (Native.cs).
The enumeration itself it's done through setupapi.dll functions. It browse all the installed devices and filters what it's need it.
So... I think it's a security issue to execute kernel32.dll code directly from a web-app in IIS with anonymous authentication, don't you?
If you really need to communicate with that HID (who knows maybe it's a temperature sensor, or something else) I would do a separate Windows service and the IIS hosted web app would communication through WCF with this service. This service would like a proxy.

Put the same code in a console application and run it. That will help you verify if it's your code or environment.
If it's environment, try using Process Monitor to see if there are any hidden access errors. Also try enumerating all devices, not just looking for the one device you're after, just to see if you can do it in ASP.NET.

#Chase, unless this is an experiment - it is best not to attempt connecting to a device from IIS process. [It's a Pandora's box if you start down this path].
Best way to do this is to have another (WCF) service as proxy to the device and expose just what you need out of the service, hook it up with your app. Feel free to ask for an example if you think that would help.
I +1 #garzanti.