.NET 6 and WINUI3 fails to start Unable to load DLL 'Microsoft.ui.xaml.dll'

[devlead]

Describe the bug

When running WINUI3 on Windows 10 ( 21H1 19043.1083 ) looks like the application never launches, but is application crashes with the below error in the event log

CoreCLR Version: 6.0.21.52210
.NET Version: 6.0.0
Description: The process was terminated due to an unhandled exception.
Exception Info: System.DllNotFoundException: Unable to load DLL 'Microsoft.ui.xaml.dll' or one of its dependencies: The specified module could not be found. (0x8007007E)

Steps to reproduce the bug

Packaged

1. Install Windows 10 21H1 19043.1083
2. Install the latest Microsoft.WindowsAppRuntime.Redist.1.0.0
3. Install MSIX dependencies
4. Install application MSIX
5. Launch the application
6. Application never launches (well crashes)

Unpackaged,

1. Install Windows 10 21H1 19043.1083
2. Install the latest Microsoft.WindowsAppRuntime.Redist.1.0.0
3. Copy compiled output
4. Launch the application
5. Application never launches (well crashes)

Packaged

1. Install Windows 10 21H2 2200.194
2. Install the latest Microsoft.WindowsAppRuntime.Redist.1.0.0
3. Install MSIX dependencies
4. Install application MSIX
5. Launch the application
6. Application never launches (well crashes)

Unpackaged,

1. Install Windows 10 21H2 2200.194
2. Install the latest Microsoft.WindowsAppRuntime.Redist.1.0.0
3. Copy compiled output
4. Launch the application
5. Application never launches (well crashes)

Expected behavior

For the application to launch.

Screenshots

No response

IDE

Visual Studio 2022

NuGet package version

Microsoft.WindowsAppSDK 1.0.0-preview3

Project type

• Packaged
• Unpackaged

Windows version

Windows 11 (22000), May 2021 Update (19043)

Additional context

No response

[kmgallahan]

CommunityToolkit/WindowsCommunityToolkit#3998 (comment)

microsoft/microsoft-ui-xaml#4591

[devlead]

Currently, get same issue with .NET 5 too though

CoreCLR Version: 5.0.1221.52207
.NET Version: 5.0.12
Description: The process was terminated due to an unhandled exception.
Exception Info: System.DllNotFoundException: Unable to load DLL 'Microsoft.ui.xaml.dll' or one of its dependencies: The specified module could not be found. (0x8007007E)
   at .Program.XamlCheckProcessRequirements()

Works on a Machine with Visual Studio and Visual Studio Extension installed.

[devlead]

Seems like others are having similar issues #974

[MikeHillberg]

I've seen that when the VCRedist wasn't installed on the target machine, which would explain why you don't see it on a machine with VS installed. Xaml.dll is generally the first runtime DLL to get loaded (trying to get static APIs from the Application class), so multiple install issues can show up with that message.

[stewienj]

@MikeHillberg Thanks, that was the solution to this problem.

[devlead]

@MikeHillberg this indeed sorted the issue 👍

[stewienj]

I think the problem here is the assumption that you can just xcopy your build output to another PC and run it when you put this in your project file:

<!-- This bundles the .NET Core libraries -->
<SelfContained>true</SelfContained>
<!-- This bundles the WinUI3 components -->
<WindowsAppSDKSelfContained>true</WindowsAppSDKSelfContained>

I see a few potential fixes for people running into this problem:

• The app should detect the missing C++ runtime DLLs and throw up a message, or log a message stating the C++ runtime needs to be installed.
• There should be a nuget package available from Microsoft that allows you to bundle the C++ runtime DLLs with your app.
• There could be a project file flag that copies the required DLLs to the build directory

[MikeHillberg]

Yes, is WRT the .NET runtime, not the WindowsAppSDK runtime.

[bryaan]

I'm having this issue as well and don't know what the solution is. I already have the Redistributable.

[yshteinm]

When I run Packaged app on my machine it works. When I run Unpackaged app it doesn't. When I run exe from console it doesn't work. When I deploy an app to another machine it doesn't work. When I say it doesn't work it means I am getting an error either in Event Viewer or dialog box "Unable to load DLL 'Microsoft.ui.xaml.dll' or one of its dependencies"
I am running Released version 1.0.0