Add a Single-Instance option for WinUI 3

[Leisvan]

Is your feature request related to a problem? Please describe.

WinUI apps are multi-instance by default, and it isn't straightforward to make an app single-instance.

Describe the solution you'd like

If the TemplateStudio had a Single-Instance option for WinUI that would save us all some time and effort.

Describe alternatives you've considered

No response

Additional context

No response

Applies to the following platforms:

• WinUI
• WPF
• UWP

[mikebattista]

Single-instance samples are shown at https://learn.microsoft.com/en-us/windows/apps/windows-app-sdk/applifecycle/applifecycle-instancing#how-the-windows-app-sdk-instancing-differs-from-uwp-instancing.

Have you been able to get that working?

[Leisvan]

I get it working (kind of). But it would be quite a boost if TemplateStudio comes with an option to setup a Single-Instance app.

[mikebattista]

Can you share your code?

There's quite a few ways to handle things so there'd need to be a canonical way to handle it that most people would want to put it in the templates.

The samples seem pretty simple for the basic case of redirecting all instances to another single instance.

[snandaworld]

Single-instance samples are shown at https://learn.microsoft.com/en-us/windows/apps/windows-app-sdk/applifecycle/applifecycle-instancing#how-the-windows-app-sdk-instancing-differs-from-uwp-instancing.

Have you been able to get that working?

I have been able to get it working with a Blank WinUI Project app, But when I try to make the App single instanced with the project which is created using Templated studio is failing to raise OnActivated() event.

It goes well till keyinstace.RedirectActivationToAsync(args).AsTask().Wait();

After this line of code, execution won't continue and throws an Aggregate exception.

OnActivated() event won't be triggerred forever.

[tomysaw]

https://blogs.windows.com/windowsdeveloper/2022/01/28/making-the-app-single-instanced-part-3/
This one also helps but contains an issue. Program.Main must remain synchronous (static void Main) otherwise it loses [STAThread]