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Creating WinUI in VS 2026, Difference between Blank App (Package) and Blank App (Package with WAPP)

Michael 146 Reputation points
2025-09-25T12:34:36.44+00:00

I'm trying to get my first WinUI to compile and run in C# using the VS 2026 Insiders release. I'm running into some snags using the stock workloads. I have the WinUI application development workload checked, and even have Windows Universal CRT SDK installed (because during one of the compiles it said it was missing)

I created a new project using WinUI Blank App (Packaged) workload. It creates a solution with a single project. I can run it in the debugger and a window opens.

I then created a new project using WinUI Blank App (Packaged with Windows Application Packaging Project). This creates a solution with 2 projects, the main app and another I recognize as the WAPP packing project (I've done this with WPF). When I try to run this in the debugger, I can try to start from the main app or the WAPP project(Package). If I start from the WAPP (which is identified as Package), I get a compile error : "Could not find SDK "Microsoft.UniversalCRT.Debug, Version=10.0.26100.0". If I try to start from the main app I get a runtime (I think) error that says: "System.Runtime.InteropServices.COMException HResult=0x80040154 Message=Class not registered (0x80040154 (REGDB_E_CLASSNOTREG))"

When using the WinUI Blank App (Packaged with Windows Application Packaging), I can never get the app to ever open in the debugger. I'm not modifying the code in any way.

So, I have a few of questions:

How can I get the stock WinUI Blank App (Packaged with Windows Application Packaging Project) to run from the debugger? I've made no modification to the code

Do I want to run the app from the main project in the solution (like I would for WPF) or from the project that says (Package)?

What's the difference in workloads other than one has a WAPP project and the other doesn't. I like the WAPP because (if it's the same as it would be when packaging a WPF app) you get a nice little web page, the installer app and the compiled app.

Developer technologies | Visual Studio | Debugging
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  1. Surya Amrutha Vaishnavi Lanka (INFOSYS LIMITED) 810 Reputation points Microsoft External Staff
    2025-09-26T11:22:28.5766667+00:00

    Thanks for reaching out, here are steps which are helpful

    1. Running the App from Debugger: For projects created with the "WinUI Blank App (Packaged with Windows Application Packaging Project)" template, you need to run the app from the WAPP project. If you’re getting errors while trying to run it, check the project properties of the WAPP project to ensure it’s correctly set up, and that all necessary SDK components are installed.
    2. Dealing with the Errors: The compile error regarding "Microsoft.UniversalCRT.Debug" could indicate that you might be missing the required Universal CRT SDK components or that the SDK is not correctly referenced. Make sure that you have the correct version of the Windows SDK installed.
    3. Difference Between Project Types: The "Blank App (Packaged)" creates a single project that includes everything you need to build an MSIX package without needing a separate packaging project.The "Blank App (Packaged with WAPP)" includes a separate Windows Application Packaging Project, which is ideal if you need multiple executables or more advanced packaging scenarios (like custom installer pages).

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