Mono MSBuild error after installing reference assemblies Ubuntu 18.04 - msbuild

Question

I would like to build a .net framework 4.7.2 project in Mono on Ubuntu 18.04
I installed mono-devel according to this guide:
https://www.mono-project.com/download/stable/
After installing and trying to run msbuild on one of my projects, I get this error:
/usr/lib/mono/msbuild/15.0/bin/Microsoft.Common.CurrentVersion.targets(1195,5): error MSB3644: The reference assemblies for framework ".NETFramework,Version=v4.7.2" were not found. To resolve this, install the SDK or Targeting Pack for this framework version or retarget your application to a version of the framework for which you have the SDK or Targeting Pack installed. Note that assemblies will be resolved from the Global Assembly Cache (GAC) and will be used in place of reference assemblies. Therefore your assembly may not be correctly targeted for the framework you intend.
I found a reference assemblies package which I installed:
mono-reference-assemblies-4.0
After installing the package and running the build again, I am getting the following error:
MSBUILD : error MSB1025: An internal failure occurred while running MSBuild.
System.IO.FileNotFoundException: Could not load file or assembly 'System.Runtime.InteropServices.RuntimeInformation, Version=4.0.1.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies.
File name: 'System.Runtime.InteropServices.RuntimeInformation, Version=4.0.1.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'
at Microsoft.Build.Shared.BuildEnvironmentHelper.get_Instance () [0x00017] in <0fd2831d9cb34830af9027441f77a417>:0
at Microsoft.Build.Utilities.Traits.get_Instance () [0x00000] in <0fd2831d9cb34830af9027441f77a417>:0
at Microsoft.Build.CommandLine.MSBuildApp.Execute (System.String commandLine) [0x000bb] in <0fd2831d9cb34830af9027441f77a417>:0
Unhandled Exception:
System.IO.FileNotFoundException: Could not load file or assembly 'System.Runtime.InteropServices.RuntimeInformation, Version=4.0.1.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies.
File name: 'System.Runtime.InteropServices.RuntimeInformation, Version=4.0.1.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'
at Microsoft.Build.Shared.BuildEnvironmentHelper.get_Instance () [0x00017] in <0fd2831d9cb34830af9027441f77a417>:0
at Microsoft.Build.Utilities.Traits.get_Instance () [0x00000] in <0fd2831d9cb34830af9027441f77a417>:0
at Microsoft.Build.CommandLine.MSBuildApp.Execute (System.String commandLine) [0x003f2] in <0fd2831d9cb34830af9027441f77a417>:0
at Microsoft.Build.CommandLine.MSBuildApp.Main () [0x00028] in <0fd2831d9cb34830af9027441f77a417>:0
[ERROR] FATAL UNHANDLED EXCEPTION: System.IO.FileNotFoundException: Could not load file or assembly 'System.Runtime.InteropServices.RuntimeInformation, Version=4.0.1.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies.
File name: 'System.Runtime.InteropServices.RuntimeInformation, Version=4.0.1.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'
at Microsoft.Build.Shared.BuildEnvironmentHelper.get_Instance () [0x00017] in <0fd2831d9cb34830af9027441f77a417>:0
at Microsoft.Build.Utilities.Traits.get_Instance () [0x00000] in <0fd2831d9cb34830af9027441f77a417>:0
at Microsoft.Build.CommandLine.MSBuildApp.Execute (System.String commandLine) [0x003f2] in <0fd2831d9cb34830af9027441f77a417>:0
at Microsoft.Build.CommandLine.MSBuildApp.Main () [0x00028] in <0fd2831d9cb34830af9027441f77a417>:0
This error occurs wherever I run msbuild from. It seems like it should be possible to build my project.
Any help would be greatly appreciated.

Answer 1

mono-reference-assemblies-4.0 package doesn't come from the stable channel of the new apt source that you added to install your new version of Mono, so you're mixing versions of Mono at runtime, which is causing those weird exceptions.
The solution is to uninstall this package and switch to unstable channel (because .NET 4.7.2 is too new for the stable one).