I have a WPF application project that includes two separate windows (in addition to the main application window), each defined in separate projects that are not included in the solution, using the <Link> tag in the .csproj file. Here's the relevant part of the project file:

<ItemGroup Label="Plugins">
  <Page Include="..\Plugin1\MainWindow.xaml">
    <Link>Plugin1\MainWindow.xaml</Link>
  </Page>
  <Compile Include="..\Plugin1\MainWindow.xaml.cs">
    <Link>Plugin1\MainWindow.xaml.cs</Link>
    <DependentUpon>MainWindow.xaml</DependentUpon>
  </Compile>

  <Page Include="..\Plugin2\MainWindow.xaml">
    <Link>Plugin2\MainWindow.xaml</Link>
  </Page>
  <Compile Include="..\Plugin2\MainWindow.xaml.cs">
    <Link>Plugin2\MainWindow.xaml.cs</Link>
    <DependentUpon>MainWindow.xaml</DependentUpon>
  </Compile>
</ItemGroup>

However, when I try to do that, I get the following compiler output:

warning CS2002: Source file 'obj\x64\Debug\MainWindow.g.cs' specified multiple times

error CS0103: The name 'InitializeComponent' does not exist in the current context

I discovered that MSBuild compiles both MainWindow.xaml files (from Plugin1 and Plugin2 folders) into the same obj\MainWindow.g.cs file, overwritting one with the other. This only happens for linked XAML pages — ordinarily, .g.cs files are placed into their respective subfolders.

Can I control where the XAML compilation result is placed? Is there any workaround besides renaming both files?

I have a WPF application project that includes two separate windows (in addition to the main application window), each defined in separate projects that are not included in the solution, using the <Link> tag in the .csproj file. Here's the relevant part of the project file:

<ItemGroup Label="Plugins">
  <Page Include="..\Plugin1\MainWindow.xaml">
    <Link>Plugin1\MainWindow.xaml</Link>
  </Page>
  <Compile Include="..\Plugin1\MainWindow.xaml.cs">
    <Link>Plugin1\MainWindow.xaml.cs</Link>
    <DependentUpon>MainWindow.xaml</DependentUpon>
  </Compile>

  <Page Include="..\Plugin2\MainWindow.xaml">
    <Link>Plugin2\MainWindow.xaml</Link>
  </Page>
  <Compile Include="..\Plugin2\MainWindow.xaml.cs">
    <Link>Plugin2\MainWindow.xaml.cs</Link>
    <DependentUpon>MainWindow.xaml</DependentUpon>
  </Compile>
</ItemGroup>

However, when I try to do that, I get the following compiler output:

warning CS2002: Source file 'obj\x64\Debug\MainWindow.g.cs' specified multiple times

error CS0103: The name 'InitializeComponent' does not exist in the current context

I discovered that MSBuild compiles both MainWindow.xaml files (from Plugin1 and Plugin2 folders) into the same obj\MainWindow.g.cs file, overwritting one with the other. This only happens for linked XAML pages — ordinarily, .g.cs files are placed into their respective subfolders.

Can I control where the XAML compilation result is placed? Is there any workaround besides renaming both files?

• c#
• wpf
• visual-studio

• Seems like you are doomed github/dotnet/wpf/issues/6290 not fixed since 2022, and no workaround – Selvin Commented Apr 1 at 20:32
• Are the namespaces used are they same or different? Which window in the app.cs is the main window? Linking files is good for DTOs where you want to share them between CLRs...I would advise instead to create custom control(s) (not the windows) and share the controls between the the two projects. – ΩmegaMan Commented Apr 1 at 23:04

1 Answer 1

As @Selvin mentioned, this is a known WPF compilation restriction. When generating .g.cs files, the WPF XAML compiler determines the output path based on the file name, and ignores the virtual directory structure defined in the <Link> tag, resulting in files with the same file name being generated to the same directory, resulting in file overwriting or conflicts. Currently there is no official attribute that directly controls the XAML generation path, so the following approach is a common practice:

1: Rename the file:

Modify the file name of the XAML file so that the generated .g.cs file name is different.

2: Avoid using links to include files:

If you want to keep the original file name, consider adding each plug-in project to the solution separately, rather than referring across projects via the <Link> tag. In this way, the generated directory of each project is independent, and there will be no conflicts in files with the same name.