WPF controls not recognized in code-behind when using new CSPROJ format

I've created a WPF application using the new CSPROJ format in Visual Studio 2017.

By

• setting the LanguageTargets,
• setting the generator for XAML files,
• setting the build action for App.Xaml,
• and forcing the debug executable

I can successfully build and run the application. However, I have an issue in that the code editor does not recognize any controls placed in the XAML, so I get erroneous errors and no intellisense in the editor.

Steps to reproduce

1. Launch VS 2017
2. Create a new "WPF App (.NET Framework)" C# project
3. Edit the csproj file to look like:

Project file:

<Project Sdk="Microsoft.NET.Sdk" ToolsVersion="15.0">
  <PropertyGroup>
    <LanguageTargets>$(MSBuildExtensionsPath)\$(VisualStudioVersion)\Bin\Microsoft.CSharp.targets</LanguageTargets>
    <TargetFramework>net45</TargetFramework>
    <ProjectGuid>{030D04DA-D603-4D4C-95F7-B6F725A6829E}</ProjectGuid>
  </PropertyGroup>
  <PropertyGroup>
    <OutputType>WinExe</OutputType>
  </PropertyGroup>
  <PropertyGroup>
    <StartupObject />
  </PropertyGroup>
  <ItemGroup>
    <ApplicationDefinition Include="App.xaml">
      <Generator>MSBuild:Compile</Generator>
      <SubType>Designer</SubType>
    </ApplicationDefinition>
    <Page Include="MainWindow.xaml">
      <SubType>Designer</SubType>
      <Generator>MSBuild:Compile</Generator>
    </Page>
    <Compile Update="**\*.xaml.cs" SubType="Designer" DependentUpon="%(Filename)" />
  </ItemGroup>
  <ItemGroup>
    <Reference Include="PresentationCore" />
    <Reference Include="PresentationFramework" />
    <Reference Include="System.Xaml" />
    <Reference Include="WindowsBase" />
  </ItemGroup>
</Project>

4. Add a button called "button1" to MainWindow.xaml as below:

MainWindow.xaml

<Window x:Class="WpfApp1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp1"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <Button Name="button1" Width="100" Height="50">Click me!</Button>
    </Grid>
</Window>

5. Try and set the button caption in code in "MainWindow.xaml.cs".

You will see that intellisense does not recognise that the button is defined:

However, the project builds and runs successfully (note you will need to run the executable manually - F5 doesn't work...)