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How can I simultaneously load 5.0 and 4.7.2 projects in Rider?

I have a .NET solution containing both net5.0 and v4.7.2 projects. It opens as expected in Visual Studio on Windows. But when I open it in Rider on Ubuntu I get assembly errors from one or the other framework. (Rider 2021.1.3 on Ubuntu 20.04.2 LTS installed from Snap Store.)

I have installed latest Stable Mono per https://www.mono-project.com/download/stable/#download-lin-ubuntu

$ mono --version
Mono JIT compiler version 6.12.0.122 (tarball Mon Feb 22 17:33:28 UTC 2021)
Copyright (C) 2002-2014 Novell, Inc, Xamarin Inc and Contributors. www.mono-project.com
    TLS:           __thread
    SIGSEGV:       altstack
    Notifications: epoll
    Architecture:  amd64
    Disabled:      none
    Misc:          softdebug 
    Interpreter:   yes
    LLVM:          yes(610)
    Suspend:       hybrid
    GC:            sgen (concurrent by default)

I have installed latest stable .NET SDK from the Snap store.

$ dotnet --version
5.0.301

In Rider I can choose between MSBuild 15.0 (from /usr/lib/mono) or 16.0 (from /snap/dotnet-sdk). This setting affects all projects in the solution.

Use MSBuild version: 15.0 or 16.0

If I pick 15.0 (Mono) then net5.0 projects fail (see message below) and v4.7.2 load correctly.

[MSB3644] The reference assemblies for .NETFramework,Version=v5.0 were not found. To
resolve this, install the Developer Pack (SDK/Targeting Pack) for this framework version
or retarget your application. You can download .NET Framework Developer Packs
at https://aka.ms/msbuild/developerpacks at (1193:5)

If I pick 16.0 (SDK) then net5.0 projects load correctly but v4.7.2 fail with:

[MSB3644] The reference assemblies for .NETFramework,Version=v4.7.2 were not found.
To resolve this, install the Developer Pack (SDK/Targeting Pack) for this framework
version or retarget your application. You can download .NET Framework Developer Packs
at https://aka.ms/msbuild/developerpacks at (1216:5)

How can I resolve this so that net5.0 and v4.7.2 projects in the same solution both load without reference errors in Rider on Ubuntu?

Solution

  • You have to install reference assemblies into .NET project which targets net472 (or any other) full framework. More specifically, this NuGet package: https://www.nuget.org/packages/Microsoft.NETFramework.ReferenceAssemblies/

    For more info you can read one of articles about .net reference assemblies, for example this one: https://andrewlock.net/using-reference-assemblies-to-build-net-framework-libararies-on-linux-without-mono/