Reference Windows only project from NET MAUI

I have been working on tool that is done using NET MAUI. Now I would like to automate Windows UI, but I can't figure out how to do that. I have tried to download FlaUI NuGet, but can't get it working as it requires project to be Net7.0-windows. So I have created new project with reference to Net7.0-windows, but then my references in Net Maui get corrupted.

MauiApp1.csproj (project):

<Project Sdk="Microsoft.NET.Sdk">

    <PropertyGroup>
        <TargetFrameworks>net7.0-android;net7.0-ios;net7.0-maccatalyst</TargetFrameworks>
        <TargetFrameworks Condition="$([MSBuild]::IsOSPlatform('windows'))">$(TargetFrameworks);net7.0-windows10.0.19041.0</TargetFrameworks>
        <!-- Uncomment to also build the tizen app. You will need to install tizen by following this: https://github.com/Samsung/Tizen.NET -->
        <!-- <TargetFrameworks>$(TargetFrameworks);net7.0-tizen</TargetFrameworks> -->
        <OutputType>Exe</OutputType>
        <RootNamespace>MauiApp1</RootNamespace>
        <UseMaui>true</UseMaui>
        <SingleProject>true</SingleProject>
        <ImplicitUsings>enable</ImplicitUsings>

        <!-- Display name -->
        <ApplicationTitle>MauiApp1</ApplicationTitle>

        <!-- App Identifier -->
        <ApplicationId>com.companyname.mauiapp1</ApplicationId>
        <ApplicationIdGuid>67771146-3ce8-452f-860b-3669d8a9e4a0</ApplicationIdGuid>

        <!-- Versions -->
        <ApplicationDisplayVersion>1.0</ApplicationDisplayVersion>
        <ApplicationVersion>1</ApplicationVersion>

        <SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'ios'">11.0</SupportedOSPlatformVersion>
        <SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'maccatalyst'">13.1</SupportedOSPlatformVersion>
        <SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'android'">21.0</SupportedOSPlatformVersion>
        <SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'windows'">10.0.17763.0</SupportedOSPlatformVersion>
        <TargetPlatformMinVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'windows'">10.0.17763.0</TargetPlatformMinVersion>
        <SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'tizen'">6.5</SupportedOSPlatformVersion>
    </PropertyGroup>

    <ItemGroup>
        <!-- App Icon -->
        <MauiIcon Include="Resources\AppIcon\appicon.svg" ForegroundFile="Resources\AppIcon\appiconfg.svg" Color="#512BD4" />

        <!-- Splash Screen -->
        <MauiSplashScreen Include="Resources\Splash\splash.svg" Color="#512BD4" BaseSize="128,128" />

        <!-- Images -->
        <MauiImage Include="Resources\Images\*" />
        <MauiImage Update="Resources\Images\dotnet_bot.svg" BaseSize="168,208" />

        <!-- Custom Fonts -->
        <MauiFont Include="Resources\Fonts\*" />

        <!-- Raw Assets (also remove the "Resources\Raw" prefix) -->
        <MauiAsset Include="Resources\Raw\**" LogicalName="%(RecursiveDir)%(Filename)%(Extension)" />
    </ItemGroup>

    <ItemGroup>
        <PackageReference Include="Microsoft.Extensions.Logging.Debug" Version="7.0.0" />
    </ItemGroup>

</Project>

Project ClassLibrary1.csproj (project):

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>net7.0-windows</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="FlaUI.Core" Version="4.0.0" />
    <PackageReference Include="FlaUI.UIA3" Version="4.0.0" />
  </ItemGroup>

</Project>

Currently if:

I get following errors:

My question is How to reference ClassLibrary1.csproj in MauiApp1.csproj in NET MAUI? Is there some way to get this setup working?

Solution

If your ClassLibrary1 project going to support all platforms then you should add this lines to your ClassLibrary1.cspoj file too.

<TargetFrameworks>net7.0-android;net7.0-ios;net7.0-maccatalyst</TargetFrameworks>
<TargetFrameworks Condition="$([MSBuild]::IsOSPlatform('windows'))">$(TargetFrameworks);net7.0-windows10.0.19041.0</TargetFrameworks>

If your ClassLibrary1 project going to support just windows then you can do two things;

If your MAUI project just going to run on windows only, on your MauiApp1.csproj file you should delete these lines;

<TargetFrameworks>net7.0-android;net7.0-ios;net7.0-maccatalyst</TargetFrameworks>

<SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'ios'">11.0</SupportedOSPlatformVersion>
<SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'maccatalyst'">13.1</SupportedOSPlatformVersion>
<SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'android'">21.0</SupportedOSPlatformVersion>
<SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'tizen'">6.5</SupportedOSPlatformVersion>

If your MAUI App going to support other platforms at the same time, you should add your platform specific libraries separate. I am using this for my multiplatform MAUI apps.

Solution Explorer > Your MAUI Project > Dependencies > Right Click Your Platform > Add reference

then open your MauiApp1.csproj file, find your reference and add an condition to your reference. Your reference should be like this at the end;
```
<ItemGroup Condition="$(TargetFramework.Contains('-windows')) != false ">
  <ProjectReference Include="..\MauiLib1\MauiLib1.csproj" />
</ItemGroup>
```

EXAMPLE

I've made an example. I created a MAUI project named MauiApp1 and a class library named MauiLib1. MauiLib1 only supports Windows platform and MauiApp1 supports all platforms. I've added MauiLib1 to MauiApp1 but for only Windows platform. Required .csproj files and platform specific codes can be seen below.

MauiApp1.csproj

 <PropertyGroup>
     <TargetFrameworks>net7.0-android;net7.0-ios;net7.0-maccatalyst</TargetFrameworks>
     <TargetFrameworks Condition="$([MSBuild]::IsOSPlatform('windows'))">$(TargetFrameworks);net7.0-windows10.0.19041.0</TargetFrameworks>

     <SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'ios'">11.0</SupportedOSPlatformVersion>
     <SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'maccatalyst'">13.1</SupportedOSPlatformVersion>
     <SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'android'">21.0</SupportedOSPlatformVersion>
     <SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'windows'">10.0.17763.0</SupportedOSPlatformVersion>
     <TargetPlatformMinVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'windows'">10.0.17763.0</TargetPlatformMinVersion>
     <SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'tizen'">6.5</SupportedOSPlatformVersion>
 </PropertyGroup>

 <ItemGroup Condition="$(TargetFramework.Contains('-windows')) != false ">
   <ProjectReference Include="..\MauiLib1\MauiLib1.csproj" />
 </ItemGroup>

MauiLib1.csproj

 <PropertyGroup>
     <TargetFrameworks Condition="$([MSBuild]::IsOSPlatform('windows'))">$(TargetFrameworks);net7.0-windows10.0.19041.0</TargetFrameworks>

     <SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'windows'">10.0.17763.0</SupportedOSPlatformVersion>
     <TargetPlatformMinVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'windows'">10.0.17763.0</TargetPlatformMinVersion>
 </PropertyGroup>

A simple class in MauiLib1 project. So we can make a test.

 public static class MauiLib1TestClass
 {
     public static string testString = "ehehehe";
 }

Changed MauiApp1 project's default MainPage.xaml.cs code a little bit. Here you can see Windows specific codes. Without these conditions your app will crash. Because there will not be a reference for that platform.

 #if WINDOWS
 using MauiLib1;
 #endif

 public partial class MainPage : ContentPage
 {
     int count = 0;

     public MainPage()
     {
         InitializeComponent();
     }

     private void OnCounterClicked(object sender, EventArgs e)
     {
         count++;

         if (count == 1)
             CounterBtn.Text = $"Clicked {count} time";
 #if WINDOWS
         else if (count == 3)
             CounterBtn.Text = MauiLib1TestClass.testString;
 #endif
         else
             CounterBtn.Text = $"Clicked {count} times";

         SemanticScreenReader.Announce(CounterBtn.Text);
     }
 }

After 3 clicks, you'll see our string in the button and here it's solution explorer's screenshot. As you can see reference added for windows only.

Note 1

Don't forget to change your current platform on the Visual Studio. It's very important. Otherwise, your platform specific codes will not be compiled.

Note 2

I deleted the parts unrelated to the question from the code. So everyone can see clearly what I've changed.

Note 3

If your library supports more than one platform you can add more conditions to your reference in the .csproj file.