.NET Core 3 support request

[dam5s]

Description

I would like to use FsXaml with .NET Core 3
.NET Core 3 brings support for WPF, but it doesn't seem to work with FsXaml

Repro steps

Please provide the steps required to reproduce the problem

Using the latest preview for .NET Core 3 -

1. Create a new dotnet core 3.0 application with WPF support -

project.fsproj

<Project Sdk="Microsoft.NET.Sdk.WindowsDesktop">

    <PropertyGroup>
        <OutputType>WinExe</OutputType>
        <TargetFramework>netcoreapp3.0</TargetFramework>
        <RootNamespace>MyNamespace</RootNamespace>
        <UseWPF>true</UseWPF>
    </PropertyGroup>

    <ItemGroup>
        <PackageReference Include="Elmish.WPF" Version="3.1.0"/>
        <PackageReference Include="FsXaml.Wpg" Version="3.1.6"/>
    </ItemGroup>
</Project>

2. Add a XAML file to the project.

3. Build the project.

Expected behavior

Project builds and I can start using the Type provider for the XAML file in my code.

Actual behavior

Build outputs an error as follows

C:\Program Files\dotnet\sdk\3.0.100-preview8-013656\Sdks\Microsoft.NET.Sdk.WindowsDesktop\targets\Microsoft.WinFX.targets(243,9): error MC1000: Unknown build error, 'Object reference not set to an instance of an object.'  [C:\Users\dam5s\workspace\epub-desktop\epub-desktop\epub-desktop.fsproj]  

Known workarounds

None that I know of. I'm using a C# project with my XAML files instead.

Related information

• Windows 10 Pro
• Latest stable version
• 3.0.100-preview8-013656

[ReedCopsey]

The plan was to update this after .net core 3 RTM is released. I'm open to a PR in a branch in the meantime, however.

[dam5s]

Awesome thanks!

[miegir]

By the way, this error message is the MS XAML compiler bug. It is going to throw error that F# is not supported, but on the way to do so this error occurs.

[TheJayMann]

looking at the network for this project, I found this branch which appears to add .NET Core 3 support. The branch is listed as testing, so I don't know how complete it is. Assuming it isn't yet complete, it appears to at least be a good starting point.

https://github.com/amazingant/FsXaml/tree/net-core-3-testing

[allykzam]

Came here looking for something else and noticed @TheJayMann had linked my test branch. It's been ages since I touched that branch, so I'm not sure how well I had it working -- but I did have a separate repository that successfully runs a ported .NET Framework 4.5 application.

@ReedCopsey: I can pass along my working code if you want to dig around at it, but due to typical corporate restrictions, I'm not able to share my changes in a PR.

[ReedCopsey]

I'd definitely be curious to see what you did - though I'm happy to poke around your repo, as well. Right now, I don't have the bandwidth to do this port (even though I do want to make it happen at some point), but am hoping I can work on it "soonish"

[allykzam]

Stripped out all of my compiled binaries and left out the sample application I mentioned (internal application from work), and put what was left here: https://github.com/amazingant/FsXamlAgain

[Kavignon]

What's the current progress on this? @dam5s

[mattstermiller]

I took the project files and other changes from @amazingant 's repo that he linked above, applied them in a branch on my fork, and worked with it to get as far as I could.

Here is the progress I was able to make:

• The core projects of this library, FsXaml.Wpf and FsXaml.Wpf.TypeProvider, have the new sdk project file format and target both netcoreapp3.0 and net45. They build and pass tests.
• The FsXaml.Wpf.Blend project has the new sdk project file format but only targets net45 since its dependency System.Windows.Interactivity.WPF is only compatible with .NET framework. It was last updated in 2013.
• 3 of the demo projects build with Visual Studio 2019 and run. 1 more builds but crashes on startup with a XamlParseException. The other 2 fail to build with "The provided method is marked as an abstract method; therefore, it should not define an implementation" and "Cannot inherit a sealed type" errors. I don't know how to fix these since the TypeProviders SDK seems to have changed quite a bit since the last release of FsXaml and I don't know if there were fundamental design changes regarding generating sealed vs. abstract types.

I need guidance on how to fix the demo apps or possibly the library to get this working.

Also, I noticed that the FAKE build script is very out-of-date. I was unable to use it and resorted to using paket, the dotnet SDK, and VS (and for building the demo projects, manually copying the library DLLs to the bin folder).

[BillHally]

@mattstermiller You need to replace the use of System.Windows.Interactivity with Microsoft.Xaml.Behaviors.Wpf.

See https://devblogs.microsoft.com/dotnet/open-sourcing-xaml-behaviors-for-wpf for details.

[mattstermiller]

Thank you, @BillHally! That resolves the issue with upgrading the Blend project and now I've got all 3 library projects targeting netcoreapp3.0 and net45.

I still need help with the demo projects.

[MatthijsPrent]

Hallo,

Is there any progress on this, or any plan to finish the upgrade to .Net Core? We would like to upgrade our project to .Net Core, but FsXaml seems to be a blockage at this moment.

[xp44mm]

request to support latest version, the fsproj file like this:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>WinExe</OutputType>
    <TargetFramework>net7.0-windows</TargetFramework>
    <UseWPF>true</UseWPF>
    <UseWindowsForms>False</UseWindowsForms>
  </PropertyGroup>

  <ItemGroup>
    <Resource Include="FirstMetroWindow.xaml" />
    <Resource Include="App.xaml" />
    <Compile Include="FirstMetroWindow.fs" />
    <Compile Include="App.fs" />
  </ItemGroup>


  <ItemGroup>
    <PackageReference Include="FsXaml.Wpf" Version="3.1.6" />
    <PackageReference Include="MahApps.Metro" Version="2.4.9" />
    <PackageReference Include="System.Reactive" Version="5.0.0" />
  </ItemGroup>

</Project>