Add .targets to validate the Windows SDK version

src/CommunityToolkit.Mvvm/CommunityToolkit.Mvvm.WindowsSdk.targets

@@ -0,0 +1,77 @@
+<Project>
+
+  <PropertyGroup>
+
+    <!-- Verification of the Windows SDK package version is enabled by default-->
+    <MvvmToolkitEnableWindowsSdkPackageVersionValidation Condition="'$(MvvmToolkitEnableWindowsSdkPackageVersionValidation)' == ''">true</MvvmToolkitEnableWindowsSdkPackageVersionValidation>
+
+    <!--
+      Wired up the Windows SDK package version verification target, if enabled.
+      This only applies to TFMs targeting Windows 10 or later.
+    -->
+    <ResolveReferencesDependsOn Condition="'$(MSBuildProjectExtension)' == '.csproj' AND
+                                           '$(MvvmToolkitVerifyWindowsSdkPackageVersion)' != 'false' AND
+                                           '$(MvvmToolkitEnableWindowsSdkPackageVersionValidation)' != 'false' AND
+                                           $([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net8.0-windows10.0.17763.0'))">
+      $(ResolveReferencesDependsOn);MvvmToolkitVerifyWindowsSdkPackageVersion
+    </ResolveReferencesDependsOn>
+  </PropertyGroup>
+
+  <!-- Custom target to verify the Windows SDK package version -->
+  <Target Name="MvvmToolkitVerifyWindowsSdkPackageVersion" DependsOnTargets="ResolveAssemblyReferences">
+    <PropertyGroup>
+
+      <!--
+        The minimum build versions for the Windows SDK package. We keep track of up to 3 different versions:
+          - The minimum Windows SDK package for which we don't want to emit a build error.
+          - The recommended Windows SDK package for UWP projects using the .NET 9 SDK (with UWP XAML projections).
+          - The recommended Windows SDK package for WindowsAppSDK projects (ie. without UWP XAML projections). 
+      -->
+      <_MvvmToolkitWindowsSdkPackageMinBuild>38</_MvvmToolkitWindowsSdkPackageMinBuild>
+      <_MvvmToolkitWindowsSdkPackageRecommendedUwpBuild>39</_MvvmToolkitWindowsSdkPackageRecommendedUwpBuild>
+      <_MvvmToolkitWindowsSdkPackageRecommendedWindowsAppSDKBuild>41</_MvvmToolkitWindowsSdkPackageRecommendedWindowsAppSDKBuild>
+
+      <!-- Switch on the recommended one based on configuration -->
+      <_MvvmToolkitWindowsSdkPackageRecommendedBuild>$(_MvvmToolkitWindowsSdkPackageMinBuild)</_MvvmToolkitWindowsSdkPackageRecommendedBuild>
+      <_MvvmToolkitWindowsSdkPackageRecommendedBuild Condition="'$(UseUwp)' == 'true'">$(_MvvmToolkitWindowsSdkPackageRecommendedUwpBuild)</_MvvmToolkitWindowsSdkPackageRecommendedBuild>
+      <_MvvmToolkitWindowsSdkPackageRecommendedBuild Condition="'$(UseUwp)' != 'true'">$(_MvvmToolkitWindowsSdkPackageRecommendedWindowsAppSDKBuild)</_MvvmToolkitWindowsSdkPackageRecommendedBuild>
+    </PropertyGroup>
+    <ItemGroup>
+
+      <!-- If 'WindowsSdkPackageVersion' is explicitly set, validate against that -->
+      <_MvvmToolkitWindowsSdkPackage Include="$(WindowsSdkPackageVersion)" Condition="'$(WindowsSdkPackageVersion)' != ''">
+        <Referenced>$(WindowsSdkPackageVersion)</Referenced>
+        <Required>10.0.$([System.Version]::Parse("$(WindowsSdkPackageVersion.Split('-')[0])").Build).$(_MvvmToolkitWindowsSdkPackageMinBuild)</Required>
+        <Recommended>10.0.$([System.Version]::Parse("$(WindowsSdkPackageVersion.Split('-')[0])").Build).$(_MvvmToolkitWindowsSdkPackageRecommendedBuild)</Recommended>
+      </_MvvmToolkitWindowsSdkPackage>
+
+      <!-- Otherwise, validate against the framework reference package -->
+      <_MvvmToolkitWindowsSdkPackage
+        Include="@(ResolvedFrameworkReference)"
+        Condition="'$(WindowsSdkPackageVersion)' == '' AND '@(ResolvedFrameworkReference)' != '' AND '%(Identity)' == 'Microsoft.Windows.SDK.NET.Ref'">
+        <Referenced>%(ResolvedFrameworkReference.TargetingPackVersion)</Referenced>
+        <Required>10.0.$([System.Version]::Parse("%(ResolvedFrameworkReference.TargetingPackVersion)").Build).$(_MvvmToolkitWindowsSdkPackageMinBuild)</Required>
+        <Recommended>10.0.$([System.Version]::Parse("%(ResolvedFrameworkReference.TargetingPackVersion)").Build).$(_MvvmToolkitWindowsSdkPackageRecommendedBuild)</Recommended>
+      </_MvvmToolkitWindowsSdkPackage>
+
+      <!-- Check whether the referenced Windows SDK package is compatible -->
+      <_MvvmToolkitCompatibleWindowsSdkPackages
+        Include="@(_MvvmToolkitWindowsSdkPackage)"
+        Condition="'@(_MvvmToolkitWindowsSdkPackage)' != '' AND $([MSBuild]::VersionGreaterThanOrEquals(%(Referenced), %(Required)))" />
+    </ItemGroup>
+    <PropertyGroup>
+
+      <!-- Extract the required and recommended Windows SDK package version (to show if the one in use is not compatible) -->
+      <_MvvmToolkitWindowsSdkPackageRequired>@(_MvvmToolkitWindowsSdkPackage->'%(Required)')</_MvvmToolkitWindowsSdkPackageRequired>
+      <_MvvmToolkitWindowsSdkPackageRecommended>@(_MvvmToolkitWindowsSdkPackage->'%(Recommended)')</_MvvmToolkitWindowsSdkPackageRecommended>
+    </PropertyGroup>
+
+    <!-- Emit an error if the Windows SDK package version isn't valid -->
+    <Error
+      Condition="'@(_MvvmToolkitCompatibleWindowsSdkPackages)' == ''"
+      Code="MVVMTKCFG0003"
+      HelpLink="https://aka.ms/mvvmtoolkit/errors/mvvmtkcfg0003"
+      Text="This version of the MVVM Toolkit requires 'Microsoft.Windows.SDK.NET.Ref' version '$(_MvvmToolkitWindowsSdkPackageRequired)' or later. Please update to .NET SDK 8.0.109, 8.0.305 or 8.0.402 (or later). Alternatively, use a temporary 'Microsoft.Windows.SDK.NET.Ref' reference, which can be done by setting the 'WindowsSdkPackageVersion' property in your .csproj file. For your project configuration, it is recommended to set the package version to '$(_MvvmToolkitWindowsSdkPackageRecommended)'." />
+  </Target>
+
+</Project>

src/CommunityToolkit.Mvvm/CommunityToolkit.Mvvm.csproj

@@ -99,9 +99,11 @@
     <!-- Include the custom .targets files (shared across TFMs) -->
     <None Include="CommunityToolkit.Mvvm.FeatureSwitches.targets" PackagePath="build" Pack="true" />
     <None Include="CommunityToolkit.Mvvm.SourceGenerators.targets" PackagePath="build" Pack="true" />
+    <None Include="CommunityToolkit.Mvvm.WindowsSdk.targets" PackagePath="build" Pack="true" />
     <None Include="CommunityToolkit.Mvvm.targets" PackagePath="build" Pack="true" />
     <None Include="CommunityToolkit.Mvvm.FeatureSwitches.targets" PackagePath="buildTransitive" Pack="true" />
     <None Include="CommunityToolkit.Mvvm.SourceGenerators.targets" PackagePath="buildTransitive" Pack="true" />
+    <None Include="CommunityToolkit.Mvvm.WindowsSdk.targets" PackagePath="buildTransitive" Pack="true" />
     <None Include="CommunityToolkit.Mvvm.targets" PackagePath="buildTransitive" Pack="true" />
 
     <!--

src/CommunityToolkit.Mvvm/CommunityToolkit.Mvvm.targets

@@ -4,10 +4,12 @@
   <PropertyGroup>
     <_CommunityToolkitMvvmFeatureSwitchesTargets>$(MSBuildThisFileDirectory)CommunityToolkit.Mvvm.FeatureSwitches.targets</_CommunityToolkitMvvmFeatureSwitchesTargets>
     <_CommunityToolkitMvvmSourceGeneratorsTargets>$(MSBuildThisFileDirectory)CommunityToolkit.Mvvm.SourceGenerators.targets</_CommunityToolkitMvvmSourceGeneratorsTargets>
+    <_CommunityToolkitMvvmWindowsSdkTargets>$(MSBuildThisFileDirectory)CommunityToolkit.Mvvm.WindowsSdk.targets</_CommunityToolkitMvvmWindowsSdkTargets>
   </PropertyGroup>
 
   <!-- Import all available .targets -->
   <Import Project="$(_CommunityToolkitMvvmFeatureSwitchesTargets)" />
   <Import Project="$(_CommunityToolkitMvvmSourceGeneratorsTargets)" />
+  <Import Project="$(_CommunityToolkitMvvmWindowsSdkTargets)" />
 
 </Project>