Show a warning when the tools are used with a platform-specific app

src/dotnet-ef/Properties/Resources.resx

@@ -330,6 +330,9 @@
   <data name="PrecompileQueriesWarning" xml:space="preserve">
     <value>Query precompilation is an experimental feature and should be used with caution.</value>
   </data>
+  <data name="PlatformSpecificProject" xml:space="preserve">
+    <value>Startup project '{startupProject}' targets a platform-specific framework: '{targetFrameworkValue}'. The Entity Framework Core .NET Command-line Tools might not function correctly. Implement IDesignTimeDbContextFactory&lt;&gt; to ensure design-time tools work correctly with this project. See https://aka.ms/efcore-docs-migrations-projects for more information.</value>
+  </data>
   <data name="PrefixDescription" xml:space="preserve">
     <value>Prefix output with level.</value>
   </data>

src/dotnet-ef/RootCommand.cs

@@ -106,6 +106,13 @@ protected override int Execute(string[] _)
             startupProject.AssemblyName + ".runtimeconfig.json");
         var projectAssetsFile = startupProject.ProjectAssetsFile;
 
+        if (!string.IsNullOrEmpty(startupProject.TargetPlatformIdentifier)
+            || HasPlatformInTargetFramework(startupProject.TargetFramework))
+        {
+            Reporter.WriteWarning(
+                Resources.PlatformSpecificProject(startupProject.ProjectName, startupProject.TargetFramework));
+        }
+
         var targetFramework = new FrameworkName(startupProject.TargetFrameworkMoniker!);
         if (targetFramework.Identifier == ".NETFramework")
         {
@@ -313,6 +320,18 @@ private static string GetVersion()
         => typeof(RootCommand).Assembly.GetCustomAttribute<AssemblyInformationalVersionAttribute>()!
             .InformationalVersion;
 
+    private static bool HasPlatformInTargetFramework(string? targetFramework)
+    {
+        if (string.IsNullOrEmpty(targetFramework))
+        {
+            return false;
+        }
+
+        // Check for netX.Y-Z form (e.g. net8.0-windows10.0.19041.0)
+        var dashIndex = targetFramework.IndexOf('-');
+        return dashIndex > 0 && dashIndex < targetFramework.Length - 1;
+    }
+
     private static bool ShouldHelp(IReadOnlyList<string> commands, IList<string> args)
         => args.Count == 0
             || commands.Count == 0