XamlC error after upgrading Visual Studio / SDK 6.0.2

After updating Visual Studio / SDK 6.0.2, I am seeing the following Xaml compiler errors in my WPF App:

XamlC error XFC0000 : Cannot resolve type "Application"
XamlC error XFC0000 : Cannot resolve type "Window".

I have isolated the cause of these errors to a package reference that references ‘Xamarin.Forms’. This package reference worked fine prior to installing the update.

Repro Steps

1. Create a new WPF App.
2. Add a package reference to ‘Xamarin.Forms’.
3. XAML compiler can not resolve “Application” and “Window” types.

[ThomasGoulet73]

@ebussa This looks unrelated to WPF because the XAML files in your repro are WPF XAML files but the error says that Xamarin tries to compile the files (Which it can’t, hence the errors). So it looks like the Visual Studio update made Xamarin try to compile those WPF XAML files (Xamarin tries to compile every .xaml files by default). You can opt out of the default Xamarin compilation by setting EnableDefaultXamlItems to false in your csproj.

The point that I was trying to make in my previous comment wasn’t that you shouldn’t do it, it was that it wasn’t suppose to work in the first place. By default, WPF and Xamarin will both try to compile .xaml files so you need to disable the one that you don’t use in your project.

[ebussa]

You can opt out of the default Xamarin compilation by setting EnableDefaultXamlItems to false in your csproj.

Thank you for that, it works!

...
    <EnableDefaultXamlItems>false</EnableDefaultXamlItems>
  </PropertyGroup>

I will create an issue with the third party package team and let them know about this change.