Consume C# nuget from C++/Cx with additional C# dependencies

[DominikMe]

Problem statement

It is hard to pack a C# Windows Runtime Component that has dependencies to other CLR nuget packages so that it can be consumed from a C++/Cx Universal Windows App.

Notice that this is not the typical "consume native from managed" problem but the opposite direction: an existing C++ app that needs to consume XAML controls and libraries written in C#.

The question is how to do this properly, a minimal working solution is attached. However, my approach does not feel quite right.

Details about Problem

Setup:

1. A C# Universal Windows Runtime Component project with a XAML control that has dependencies to other managed nugets. In this example, to Newtonsoft.Json.

2. A C++/Cx Universal Windows App that needs to consume the C# XAML control. The C++ project is packages.config based.

In a perfect world, declaring dependencies in the RuntimeComponent's nuspec file would lead to restoring these packages. However, nuget restore fails because it cannot install C# packages into a C++ project.

Workaround:

To make this work, I included all dependencies directly. This is tricky because it includes transitive dependencies, such as a package C in a dependency chain A -> B -> C.

After lots of reading and experimenting I added <CopyNugetImplementations>true</CopyNugetImplementations> to my RuntimeComponent's csproj which will copy all assemblies that the project depends on to the build output folder. Then in my manually crafted nuspec, I copied these additional DLLs to my package with the <file> attribute. In the targets file these dependencies are then added to the consuming project with

<None Include="$(MSBuildThisFileDirectory)..\..\ref\*.dll">
    <DeploymentContent>true</DeploymentContent>
</None>

Problems with the workaround:

This solution works but has inherent issues.

Finding which DLLs need to be copied is very tedious:

• Either include all DLLs. install the package to the C++ app, try to build and see which assemblies are rejected due to duplication
• Or include DLLs one by one, install the package, build and run the C++ app and make note of LoadAssembly runtime errors, repeat.

In the attached minimal example, I ended up having to include Newtonsoft.Json and also even System DLLs.

<file src="bin\Release\Newtonsoft.Json.dll" target="ref" />
<file src="bin\Release\System.ComponentModel.TypeConverter.dll" target="ref" />
<file src="bin\Release\System.Runtime.Serialization.Formatters.dll" target="ref" />

What is the recommended approach to redistribute CLR nuget dependencies and their transitive dependencies with a Windows Runtime Component, so that it can be consumed from a C++ UWP project?

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NuGet product used (NuGet.exe | VS UI | Package Manager Console | dotnet.exe): NuGet.exe

NuGet version (x.x.x.xxx): 4.3.0.4406

VS version (if appropriate): 15.4.2

OS version: win10 v1703 15063.674

Sample Project

UwpInteropPackaging_Example.zip

[zhili1208]

@emgarten looks like we don't have a compete support for this scenario, do you know any better way to make this work?

[emgarten]

The issue tracking support for C++ apps consuming managed assemblies is here: #5292 Please up vote and comment there.

I appreciate the detailed the write up of the issue, but at this time UWP is only using packages.config, which does not support the ref/ folder. We would like to tackle this problem directly instead of providing workarounds for the currently broken scenario.

[timg-mlbam]

I'm running into similar problems when trying to consume WinRT components in UWP JavaScript apps. (where WinRT component is written in C# but has non-WinRT C# internal dependencies like Json.NET). A solution to this would be great!