Fix: Ensure SupportedOSPlatformVersion is respected by installer when TargetPlatformMinVersion is not set

build/NuSpecs/Microsoft.WindowsAppSDK.Foundation.targets

@@ -16,6 +16,14 @@
   <Import Project="$(MSBuildThisFileDirectory)Microsoft.WindowsAppSDK.AutoInitializerCommon.targets" />
   <Import Project="$(MSBuildThisFileDirectory)Microsoft.WindowsAppSDK.AutoInitializer.CS.targets" Condition="'$(WindowsAppSdkAutoInitialize)' == 'true'"/>
 
+  <!-- Set TargetPlatformMinVersion from SupportedOSPlatformVersion if not already set -->
+  <Target Name="WindowsAppSDKSetTargetPlatformMinVersion" BeforeTargets="BeforeGenerateCurrentProjectAppxManifest">
+    <PropertyGroup>
+      <!-- If TargetPlatformMinVersion is not set but SupportedOSPlatformVersion is, use SupportedOSPlatformVersion -->
+      <TargetPlatformMinVersion Condition="'$(TargetPlatformMinVersion)' == '' AND '$(SupportedOSPlatformVersion)' != ''">$(SupportedOSPlatformVersion)</TargetPlatformMinVersion>
+    </PropertyGroup>
+  </Target>
+
   <ItemGroup>
     <Compile Condition="'$(WindowsAppSDKAggregatePackage)' == 'true' and '$(WindowsAppSdkIncludeVersionInfo)'=='true'" Include="$(MSBuildThisFileDirectory)..\include\WindowsAppSDK-VersionInfo.cs" />
   </ItemGroup>

build/NuSpecs/WindowsAppSDK-Nuget-Common.targets

@@ -1,20 +1,30 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <!-- Copyright (c) Microsoft Corporation. All rights reserved. Licensed under the MIT License. See LICENSE in the project root for license information. -->
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+
+  <!-- Set TargetPlatformMinVersion from SupportedOSPlatformVersion if not already set -->
+  <Target Name="WindowsAppSDKSetTargetPlatformMinVersion" BeforeTargets="PrepareForBuild">
+    <PropertyGroup>
+      <!-- If TargetPlatformMinVersion is not set but SupportedOSPlatformVersion is, use SupportedOSPlatformVersion -->
+      <TargetPlatformMinVersion Condition="'$(TargetPlatformMinVersion)' == '' AND '$(SupportedOSPlatformVersion)' != ''">$(SupportedOSPlatformVersion)</TargetPlatformMinVersion>
+    </PropertyGroup>
+  </Target>
+
   <!-- Check TargetPlatformMinVersion during build to block unsupported configurations. -->
-  <Target Name="MicrosoftWindowsAppSDKCheckTargetPlatformVersion" BeforeTargets="PrepareForBuild"
+  <Target Name="MicrosoftWindowsAppSDKCheckTargetPlatformVersion" BeforeTargets="PrepareForBuild" 
+      AfterTargets="WindowsAppSDKSetTargetPlatformMinVersion"
       Condition="'$(TargetPlatformVersion)' != '' and '$(TargetPlatformMinVersion)' != '' and '$(SkipMicrosoftWindowsAppSDKCheckTargetPlatformVersion)'==''">
     <PropertyGroup>
       <MicrosoftWindowsAppSDKTargetPlatformMinCheckValue>$([System.Version]::Parse('$(TargetPlatformMinVersion)').Build)</MicrosoftWindowsAppSDKTargetPlatformMinCheckValue>
     </PropertyGroup>
     <Error
-        Text="Microsoft.WindowsAppSDK nuget package requires TargetPlatformMinVersion &gt;= 10.0.17763.0 (current project is $(MicrosoftWindowsAppSDKTargetPlatformMinCheckValue))"
+        Text="Microsoft.WindowsAppSDK nuget package requires TargetPlatformMinVersion >= 10.0.17763.0 (current project is $(MicrosoftWindowsAppSDKTargetPlatformMinCheckValue))"
         Condition="$(MicrosoftWindowsAppSDKTargetPlatformMinCheckValue) &lt; 17763" />
     <PropertyGroup>
       <MicrosoftWindowsAppSDKTargetPlatformCheckValue>$([System.Version]::Parse('$(TargetPlatformVersion)').Build)</MicrosoftWindowsAppSDKTargetPlatformCheckValue>
     </PropertyGroup>
     <Error
-        Text="Microsoft.WindowsAppSDK nuget package requires TargetPlatformVersion &gt;= 10.0.18362.0 (current project is $(MicrosoftWindowsAppSDKTargetPlatformCheckValue))"
+        Text="Microsoft.WindowsAppSDK nuget package requires TargetPlatformVersion >= 10.0.18362.0 (current project is $(MicrosoftWindowsAppSDKTargetPlatformCheckValue))"
         Condition="$(MicrosoftWindowsAppSDKTargetPlatformCheckValue) &lt; 18362" />
   </Target>
 </Project>

build/NuSpecs/WindowsAppSDK-Nuget-Native.targets

@@ -165,4 +165,12 @@
   <Import Project="$(MSBuildThisFileDirectory)..\Microsoft.WindowsAppSDK.AutoInitializerCommon.targets" />
   <Import Project="$(MSBuildThisFileDirectory)WindowsAppSDK-Nuget-Native.AutoInitializer.targets" Condition="'$(WindowsAppSdkAutoInitialize)' == 'true'"/>
 
+  <!-- Set TargetPlatformMinVersion from SupportedOSPlatformVersion if not already set -->
+  <Target Name="WindowsAppSDKSetTargetPlatformMinVersion" BeforeTargets="BeforeGenerateCurrentProjectAppxManifest">
+    <PropertyGroup>
+      <!-- If TargetPlatformMinVersion is not set but SupportedOSPlatformVersion is, use SupportedOSPlatformVersion -->
+      <TargetPlatformMinVersion Condition="'$(TargetPlatformMinVersion)' == '' AND '$(SupportedOSPlatformVersion)' != ''">$(SupportedOSPlatformVersion)</TargetPlatformMinVersion>
+    </PropertyGroup>
+  </Target>
+
 </Project>

docs/faq.md

@@ -178,6 +178,10 @@ In-box components will be supported forever in the usual way. We have no plans t
 (remove their usability) at this time. We will likely slow down or pause investment in
 the in-box components while we focus on making the Windows App SDK surface complete.
 
+## How does Windows App SDK handle SupportedOSPlatformVersion and TargetPlatformMinVersion?
+
+When using Windows App SDK with .NET projects that set both `TargetFramework` (like net8.0-windows10.0.22621.0) and `SupportedOSPlatformVersion` (like 10.0.19041.0), Windows App SDK will ensure that `TargetPlatformMinVersion` is set to match `SupportedOSPlatformVersion` if `TargetPlatformMinVersion` is not explicitly defined. This ensures that your app can be installed on all operating system versions that you've indicated support for via `SupportedOSPlatformVersion`, rather than just the OS version specified in `TargetFramework`.
+
 ## I don't see my question here!
 
 [Create an issue to ask a question or start a discussion](https://github.com/microsoft/WindowsAppSDK/issues/new/choose).