System.ArgumentException: The parameter 'frameworkName' cannot be an empty string.

[pampersrocker]

When I try to open a rather old VS 2008 Unity solution I do get the following error in VSCode and Atom:

[INFO] Starting OmniSharp at 'c:\test\test.sln'...
[INFO] Started OmniSharp from 'c:\Program Files (x86)\Microsoft VS Code\resources\app\extensions\jrieken.vscode-omnisharp\bin\omnisharp.cmd' with process id 12448...
[INFORMATION:OmniSharp.Startup] Omnisharp server running using stdio at location 'c:\test' on host 8816.
[INFORMATION:OmniSharp.Dnx.DnxPaths] Using runtime 'c:\test\.dnx\runtimes\dnx-clr-win-x86.1.0.0-rc1-update1'.
[INFORMATION:OmniSharp.Dnx.DnxProjectSystem] Scanning 'c:\test' for DNX projects
[INFORMATION:OmniSharp.Dnx.DnxProjectSystem] No project.json based projects found
[INFORMATION:OmniSharp.MSBuild.MSBuildProjectSystem] Loading project from 'c:\test\test.csproj'.
[INFORMATION:OmniSharp.MSBuild.MSBuildProjectSystem] Detecting projects in 'c:\test\test.sln'.
[INFORMATION:OmniSharp.MSBuild.MSBuildProjectSystem] Using toolset 2.0 for c:\test\test.csproj
[INFORMATION:OmniSharp.ScriptCs.ScriptCsProjectSystem] Detecting CSX files in 'c:\test'.
[INFORMATION:OmniSharp.ScriptCs.ScriptCsProjectSystem] Could not find any CSX files
[INFORMATION:OmniSharp.Startup] Solution has finished loading
[INFORMATION:OmniSharp.MSBuild.MSBuildProjectSystem] Using toolset 2.0 for c:\test\test.csproj
[WARNING:OmniSharp.MSBuild.MSBuildProjectSystem] Failed to process project file 'c:\test\test.csproj'.
System.ArgumentException: The parameter 'frameworkName' cannot be an empty string.
Parameter name: frameworkName
   at System.Runtime.Versioning.FrameworkName..ctor(String frameworkName)
   at OmniSharp.MSBuild.ProjectFile.ProjectFileInfo.Create(MSBuildOptions options, ILogger logger, String solutionDirectory, String projectFilePath, ICollection`1 diagnostics)
   at OmniSharp.MSBuild.MSBuildProjectSystem.CreateProject(String projectFilePath)
c:\test\test.csproj(0,0)
System.ArgumentException: The parameter 'frameworkName' cannot be an empty string.
Parameter name: frameworkName
   at System.Runtime.Versioning.FrameworkName..ctor(String frameworkName)
   at OmniSharp.MSBuild.ProjectFile.ProjectFileInfo.Create(MSBuildOptions options, ILogger logger, String solutionDirectory, String projectFilePath, ICollection`1 diagnostics)
   at OmniSharp.MSBuild.MSBuildProjectSystem.CreateProject(String projectFilePath)

Here's a Gist for the Minimal reproduction case (test.sln and test.csproj, fixed_test.csproj contains the workaround below): https://gist.github.com/pampersrocker/7d38b839eda1d06a4598

I've nailed down the bug to the following line:
https://github.com/OmniSharp/omnisharp-roslyn/blob/master/src/OmniSharp.MSBuild/ProjectFile/ProjectFileInfo.cs#L91 (or the other ones from the other #ifs)

Whats the purpose of the TargetFrameworkMoniker ?
I can get it working when I add a TargetFrameworkMoniker into the csproj file, see https://gist.github.com/pampersrocker/7d38b839eda1d06a4598#file-fixed_test-csproj-L14

However this should not be needed as msbuild and VS 2008 can parse and build the projects without any problems.

When I create a new ConsoleApplication Project with VS 2015, everything works as expected.

[jjuel]

I am also getting the same issue with a VS2008 project that I am trying to edit with VS Code.

[filipw]

@pampersrocker @jjuel do you have a public project that can be used to reproduce this error? thanks

[willl]

Looks like TargetFrameworkMoniker was added to VS 2010 to support multiple targeting.

https://blogs.msdn.microsoft.com/visualstudio/2010/05/19/visual-studio-managed-multi-targeting-part-1-concepts-target-framework-moniker-target-framework/

Our MSBuild project/solution support is rather preliminary and does not cater for many scenarios at present. Issue #202 details some of the other issues.

@filipw The gist @pampersrocker linked to seems to contain the relevant .csproj files that are producing the issue (the key line in his fixed version is the addition of the <TargetFrameworkMoniker>...</TargetFrameworkMoniker> line.

[pampersrocker]

@filipw Look at my gist, there is a solution file and a csproj file.