Develop Reference

Open application from Universal Windows(UWP)

So for our project, we have this app that's in the Windows Store. It is a Unity UWP app. At some point, we want to check if program X is installed on the user's machine. If yes, we want to launch it, if no we want to provide the user with a download link (or whatever.)
The app we want to launch, however, is a Unity standalone app. The user can download it from our website.
I tried multiple things. PlayerPrefs, Register checking etc. None of these really work. Register checking turned out to work decently well, but that only works between standalone apps. UWP apps seem to have no access to the Register.
Which left me thinking about URIs etc. But, I'm a complete noob regarding all of this and I have no clue how or where to start. Any help or direction is highly appreciated.
Ideal scenario:
User downloads our app from the Windows Store
Users click a button within our app
Our app checks the user's system for App X
If App X is installed, we launch it, if not we do something else
App X opens.

The UWP app cannot interact with the standalone Unity app directly.
You can write another standalone desktop “helper” app that does the actual work of checking the registry and launching the Unity app, and then make this “helper” app part of the UWP package and resubmit the package to the Windows Store.
Keep the “helper” app as simple as possible so it doesn’t have other dependencies.
Use FullTrustProcessLauncher to launch the helper app when the user clicks the button.
And the UWP app needs to have runFullTrust capability in order to use FullTrustProcessLauncher.
runFullTrust is a restricted capacity and when you submit the app to the Windows Store it is required for you to specify the reason why the capacity is necessary for your app. See this answer for more details.

how to get list of all installed apps and run them in UWP WinRT 8.1

I'm actually creating an UWP 8.1 app for one of my client.And I've got some little issue with it.At some point of my app I've to get all the names of installed app in the device and view it as a list.When the user will click on any of them, I've to launch that certain app.
I've already tried to add restricted capabilities in the app manifest but it shows a blue line when I add,
Morever I can get access to the AppData/Packages by using folderpicker somehow but don't know what to do.
The app is for WinRT surface 3 and it isn't going to store or anything it has only one user. So if anyone know any sort of solution please let me know.

The PackageManager class has the methods to enumerate all installed apps.
However, in 8.1 the PackageManager can only be used in desktop apps (e.g. WPF, Winforms, Win32). It cannot be used from a Store app on that version of the operating system.
On Windows 10 you can use the class from both Store/UWP apps as well as classic desktop apps.

Run External exe from UWP app, workaround sandboxed mode

I have a program where i want to have the ability to launch a local application (for example Spotify) from my UWP App. I have searched the web for a solution as (Process.Start()) doesn't work. As i have understood the UWP applications is kind of sandboxed for saftey and stability reasons. But is there a (simpel) way to work around this.
I only want the ability to start and close a program inside my own frame/Window. No need to interact/send/recive data between my applications and the external program

That is not possible with all apps. Some desktop apps handle protocol launches and that can be a way of launching another app. Spotify actually has a protocol registered so you could do this to launch it:
await Launcher.LaunchUriAsync(new Uri("spotify:"));

I have a program where i want to have the ability to launch a local
application (for example Spotify) from my UWP App.
You can utilize Windows.System.ProcessLauncher API.
Here is a sample about how to launch an external process (exe) from a Universal Windows Platform (UWP) app you can reference.
Make sure add systemManagement capabiity.
For more information reference Process​Launcher.

UWP : Using WPF app to get a screenshot of a specific application

I need to write an app that shows all the running UWP apps and has next to the name of the app the screen shot of that app (what it is currently doing). Very similar to this:Get a screenshot of a specific application
So I need to get handles of apps, and then as above from the handle get the screen shot of each app.
My app is a WPF C# app. So what APIs do I need to do this?

WinRT - Start an application on Windows boot?

I'm working on a Metro style application in the new WinRT (.NET 4.5) framework for Windows 8, and I was wondering if it would be possible somehow for an application (through the registry or some other means) to register itself to start up when Windows starts as well.
I haven't been able to find anything about this anywhere else, only for Windows 7 or below, with normal-style applications.

There is no way to make a Metro style application launch at boot. The user will have to invoke the application from the start screen. Metro style applications cannot be services and so launching them at boot time doesn't seem like the right approach any more than launching Microsoft Word or Adobe Photoshop at boot time would be.

Microsoft's goal with Metro-style apps is that the user is always in control. Therefore, Metro-style apps cannot activate themselves when a machine boots up. Furthermore, traditional Win32/.NET desktop code cannot interact with Metro-style apps and so cannot start a Metro-style app behind the scenes.
That said, if your app has registered itself as the handler for the rendering of its own tile, then it gets called periodically and is asked to re-render its tile's content so it should always be able to show its latest status/news/info to the user when they view their start page.

I think you could have all your star tup stuff running as a service that exposes the appropriate WinRT level connectivity. Then the user only needs to fir up the client app.
Goo separation too.