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C# - UWP open new instance of a window when middle-mouse clicking on the app's taskbar icon

Perhaps this is a silly question, however I've searched around quite a bit and not been able to find an answer related to UWP apps.
How can one trigger an instance of their app's main window to open when middle-mouse clicking the taskbar icon? Edge can do it, so I'm assuming it's possible, just not documented or frequently done.
Thanks in advance!

By default, UWP apps support only one view (window) per app at one time so when user tries to open an UWP app that is already running, system switches to the running app rather then creating a new instance.
So you have to support multiple views in your app in order to create new instance when middle-clicked on taskbar.
You can find some documentation about multiple views in UWP app on MSDN, for example in this article.

Combine two applications into one icon on taskbar

I have two applications. One is the main application and the other is the updater.
A user launches with the updater - if an update is available it will download and extract, otherwise it will just launch the main application. I used two applications for this so that I am able to overwrite the main applcation.
The issue is that the users have pinned the "Launcher" application on their taskbar, but when the main application launches it is not grouped under that icon and very confusing for them.
Is there any way around this?

You should be able to do that using Windows API Code Pack.
You need to use Microsoft.WindowsAPICodePack.Taskbar namespace from the Microsoft.WindowsAPICodePack.Shell assembly.
Call TaskbarManager.Instance.SetApplicationIdForSpecificWindow( window, string appId ); method. You can specify either an IntPtr windows handle if you're using WinForms, or a Window instance if you're using WPF.
Do this step in both your processes immediately after launch, and specify the same appId for both.

you can refer [ How to group my apps in windows taskbar? ] of George's answer,
by forcefully make two process share the same APP_ID(string)
simply by calling shell32!SetCurrentProcessExplicitAppUserModelID at each process's main()

It was already mentioned to set the Application user Model ID.
But then you still have the problem that when the Application is pinned, it will not pin to the Launcher. But there is also a solution for this, that the Launcher/Updater is pinned instead of the Application: Pinning to the taskbar a "chained process"

Get Application that runs a Windows Form Control

I'm making an Autocad Plugin which runs fine using Windows Forms
And I've created a user control (winforms) to replicate in any form I like in the future.
The question is
From the control's code, how do I get the instance of the application running that control?
(Probably a pure winforms problem)
Coditions:
Within the plug-in I can get the Autocad Application instance with no
problem.
This user control is meant to be in a separate assembly (dll) to be referenced in the plug-in application, so it has no direct access to the application instance.
A little explanation about the scenario:
There's a Main Assembly being run by Autocad as a plug-in.
That assembly has the Autocad application instantiated.
Now I have some useful form controls to work with Autocad, and they are in a separate assembly. (That's because I want to use them in as many different plug-ins I like).
So, Autocad runs main assembly, and main assembly runs controls of the separate assembly.
In order to work properly, those controls need to have access to the Autocad application wich is running the main assembly.
Today I use the application as a property in the controls, wich I must set before working with them. (If I forget to set that, exceptions are raised). Since I cannot have a control with a creator taking parameters.
I want the controls to detect their running application so I avoid that workaround.

Please see the following code
public class MyCommands {
[CommandMethod("NS", "TEST", "TEST", CommandFlags.Modal)]
public void TestCommand() // This method can have any name
{
Form fromAutoCADAPI = new TestForm();
Form independent1 = new TestForm();
Form independent2 = new TestForm();
//Using AutoCAD application
Autodesk.AutoCAD.ApplicationServices.Application.ShowModelessDialog(fromAutoCADAPI);
independent1.Show();
independent2.Show();
//Using Windows Forms Application
var count = System.Windows.Forms.Application.OpenForms.Count; //should be 3
Autodesk.AutoCAD.ApplicationServices.Application.ShowAlertDialog(count.ToString());
}
}
If this is what you already know, then may be you should paste some sample code that will help understand where specifically you are stuck in your code. This is the way I have used AutoCAD application and Windows Forms application. In case you wan't to grab WPF application then you can use
var application = System.Windows.Application.Current;

Windows Form as child window of an unmanaged app

I am looking for a way to embed Windows Forms applications written in C# in a C++ windows application. The native application main window is subdivided into several panes. The C# app is supposed to appear within one of those panes, i.e. the root window of the C# component (the outermost form) must be a child window of the main application.
Can this be done? If so, how?
Some additional context: To my knowledge, there are two ways to go about this. First, host the CLR in the native app by using the .net hosting APIs (ICLRRuntimeHost, etc.). Second, host the CLR by putting the windows form in an ActiveX control.
Regarding the first approach, I have managed to get the CLR started up and to load a C# assembly (thanks largely to Mattias Högström). Where I am hitting a road block is that I see no way how to tell the component I am running in the CLR that it needs to be a child of a window passed in from the C++ side.
I have also experimented with the second method (using ActiveX and thanks to Daniel Yanovsky). It almost, but only almost, works for my purposes. I can let arbitrary Windows Forms components run in a child pane of the native app. BUT they always run on the main thread of the main app. This means they use the windows message loop of the main app. MSDN says this will not work reliably since the standard Windows message loops don't meet the requirements of Windows Forms (I wanted to post the link to MSDN here but have already used up my new-user-two-link-allotment).
The exceptions to the message loop issue are, according to MSDN, Internet Explorer and MFC apps. The native app I am using as a host is definitely not Internet Explorer. Also, it uses the windows API as wrapped by wxWidgets so MFC is not (or at least not a welcome) option.
The solutions Microsoft proposes involve letting the C# components run in their own message loops on their own threads. This, at least as far as I can tell, necessarily leads back to the first approach mentioned above. So I am back to the question of getting a Windows Form to work under a passed-in parent window.
Again, I am interested in any input that clarifies the child window issue, independent of the approaches I have mentioned here. But in light of the context I could reduce the general question to two specific questions (and I would need an answer to only one of them):
Given a Windows Form hosted in an ActiveX control, how can I allow the form to run in its own message loop on its own thread?
or
Given a Windows Form running in a CLR hosted by a native app, how can I make the form be a child window of a window in the native app?

yes, it can be done. We did the same thing years ago. This is our approach: .NET control also has native window handle, we get these handles through C++/CLI and pass them to Win32, and add these handles as the children of native windows. So the .NET controls run on the main thread of the main app, the problematic part is the message loop, as you have mentioned in your question. We need route the message between the nation and .NET windows if needed. As I remembered, we fixed a lot of bugs related to this, and still there were some mysterious problem we didn't figure out.
There's anothe way: using WPF interop. http://msdn.microsoft.com/en-us/library/ms742522.aspx . According to MS, this should fix the message problems, but we didn't try this approach. You can just use Win32 to host WPF, then use WPF to host Winform.
So for your last 2 questions:
You can't. Only one message loop.
Use handle. This article talks about the handle of Windows Forms: http://blogs.msdn.com/b/jfoscoding/archive/2004/11/24/269416.aspx

How can I start a process as a child of a winform in my C# program?

I have a process that was written by WPF and I want to start it in my program. I used "process.start()" and its worked successfully. But now I want to start my process as a child of a form.

Do you mean you have a wpf usercontrol/form, and you want to display that in your winforms application?
If so, see this link: http://www.switchonthecode.com/tutorials/wpf-tutorial-using-wpf-in-winforms

You can't start process as a child of a Form! Process is just another application that is running on the computer no matter if it was build in windows forms or wpf or even assembly language.

You may mean starting new form as a child from main form?
using (ChildForm form = new ChildForm())
form.ShowDialog(this); // this refers to main form object