Microsoft.NET.Sdk.WindowsDesktop.props references System.Windows.Controls.Ribbon on .NET 4.0

[ericstj]

Problem description:
When targeting net40 from a WPF app the build emits a warning.

Actual behavior:
Warning:

C:\Program Files\dotnet\sdk\3.0.100-preview-010046\Microsoft.Common.CurrentVersion.targets(2114,5): warning MSB3267: The primary reference "System.Windows.Controls.Ribbon", which is a framework assembly, could not be resolved in the currently targeted framework. ".NETFramework,Version=v4.0". To resolve this problem, either remove the reference "System.Windows.Controls.Ribbon" or retarget your application to a framework version which contains "System.Windows.Controls.Ribbon".

Expected behavior:
No warning

Minimal repro:
dotnet new wpf
change targetframework to net40 or make it cross-target.
dotnet build

(project also attached)
net40.zip

I believe the fix is here is to put a condition on the _SDKImplicitReference items defined in Microsoft.NET.Sdk.WindowsDesktop.props.

Originally reported here: dotnet/core#2085 (comment)

[virzak]

Same issue with net35

[billhenn]

We are beginning to multi-target our WPF control assemblies to net40 and netcoreapp3.0 and are running into this warning now all over the place:

MSB3267 The primary reference "System.Windows.Controls.Ribbon", which is a framework assembly, could not be resolved in the currently targeted framework. ".NETFramework,Version=v4.0". To resolve this problem, either remove the reference "System.Windows.Controls.Ribbon" or retarget your application to a framework version which contains "System.Windows.Controls.Ribbon".

This was originally reported in January and is still occurring in .NET 3.0 preview5. Will it be fixed soon?

[vatsan-madhavan]

We should definitely fix this before p7. I worry that this will continue to be a big problem for several mainstream scenarios. This is either related to or a duplicate of #327.

/cc @nguerrera, @grubioe, @rladuca