SDK upgrade causes compile failure due to not generating VB.NET WPF code behind

Repro:

Clone [e-mail]:dotnet/project-system.git.

• Build with SDK 3.1.400-preview-015178 ✔️
• Build with SDK 5.0.100-preview.6.20318.15 ❌

Error:

src\Microsoft.VisualStudio.Editors\OptionPages\GeneralOptionPageControl.xaml.vb(45,13): error BC30451: ‘InitializeComponent’ is not declared. It may be inaccessible due to its protection level.

The project file defines the item as Page but the Properties pane shows it as None.

Potentially bad globs?

Note that this is a VB.NET file.

Also note that this worked with an earlier version of 5.0.100-preview*, but I don’t know which as it was uninstalled when I installed preview 6. I think it was preview 4.

[dsplaisted]

As I understand it, we broke SDK-style WPF projects which targeted .NET Framework, without setting UseWPF to true or using the WindowsDesktop SDK. Such projects were likely created before there was any WPF support for .NET Core. They would build with the .NET Framework version of MSBuild due to the implicit winfx.targets import, but would have failed to build with dotnet.

We should avoid breaking such projects, but we should also avoid importing multiple copies of the WPF targets. So I think the default value for ImportWinFXTargets in the SDK should be true ONLY when the TargetFrameworkIdentifier is .NETFramework, and UseWPF is not set to true. That will avoid importing the legacy winfx targets for .NET Core projects, where they won’t work, and for .NET Framework projects which are importing the newer WPF targets (which should still work when targeting .NET Framework).

[joeloff]

This should be in RC1