Add HasMetadata checks to all PEReader code paths to handle native Windows DLLs

src/Xamarin.Android.Build.Tasks/Tasks/CheckForInvalidDesignerConfig.cs

@@ -39,6 +39,9 @@ static bool HasResourceDesignerAssemblyReference (ITaskItem assembly)
 				return false;
 			}
 			using var pe = new PEReader (File.OpenRead (assembly.ItemSpec));
+			if (!pe.HasMetadata) {
+				return false;
+			}
 			var reader = pe.GetMetadataReader ();
 			return HasResourceDesignerAssemblyReference (reader);
 		}

src/Xamarin.Android.Build.Tasks/Tasks/FilterAssemblies.cs

@@ -57,6 +57,10 @@ public override bool RunTask ()
 		void ProcessAssembly(ITaskItem assemblyItem, List<ITaskItem> output)
 		{
 			using var pe = new PEReader (File.OpenRead (assemblyItem.ItemSpec));
+			if (!pe.HasMetadata) {
+				Log.LogDebugMessage ($"Skipping non-.NET assembly: {assemblyItem.ItemSpec}");
+				return;
+			}
 			var reader = pe.GetMetadataReader ();
 			// Check in-memory cache
 			var module = reader.GetModuleDefinition ();

src/Xamarin.Android.Build.Tasks/Tasks/ResolveLibraryProjectImports.cs

@@ -256,6 +256,10 @@ void Extract (
 				Log.LogDebugMessage ($"Refreshing {fileName}");
 
 				using (var pe = new PEReader (File.OpenRead (assemblyPath))) {
+					if (!pe.HasMetadata) {
+						Log.LogDebugMessage ($"Skipping non-.NET assembly: {assemblyPath}");
+						continue;
+					}
 					var reader = pe.GetMetadataReader ();
 					foreach (var handle in reader.ManifestResources) {
 						var resource = reader.GetManifestResource (handle);

src/Xamarin.Android.Build.Tasks/Utilities/MetadataResolver.cs

@@ -19,7 +19,12 @@ public MetadataReader GetAssemblyReader (string assemblyName)
 		{
 			var assemblyPath = Resolve (assemblyName);
 			if (!cache.TryGetValue (assemblyPath, out PEReader reader)) {
-				cache.Add (assemblyPath, reader = new PEReader (File.OpenRead (assemblyPath)));
+				reader = new PEReader (File.OpenRead (assemblyPath));
+				if (!reader.HasMetadata) {
+					reader.Dispose ();
+					throw new InvalidOperationException ($"Assembly '{assemblyPath}' is not a .NET assembly.");
+				}
+				cache.Add (assemblyPath, reader);
 			}
 			return reader.GetMetadataReader ();
 		}

src/Xamarin.Android.Build.Tasks/Utilities/MonoAndroidHelper.cs

@@ -353,6 +353,9 @@ public static bool HasMonoAndroidReference (ITaskItem assembly)
 				return true;
 
 			using var pe = new PEReader (File.OpenRead (assembly.ItemSpec));
+			if (!pe.HasMetadata) {
+				return false; // this is a native Windows .dll, not a .NET assembly
+			}
 			var reader = pe.GetMetadataReader ();
 			return HasMonoAndroidReference (reader);
 		}
@@ -374,6 +377,10 @@ public static bool IsReferenceAssembly (string assembly, TaskLoggingHelper log)
 		{
 			using (var stream = File.OpenRead (assembly))
 			using (var pe = new PEReader (stream)) {
+				if (!pe.HasMetadata) {
+					log.LogDebugMessage ($"Skipping non-.NET assembly: {assembly}");
+					return false;
+				}
 				var reader = pe.GetMetadataReader ();
 				var assemblyDefinition = reader.GetAssemblyDefinition ();
 				foreach (var handle in assemblyDefinition.GetCustomAttributes ()) {

src/Xamarin.Android.Build.Tasks/Utilities/ResourceDesignerImportGenerator.cs

@@ -44,6 +44,10 @@ public void CreateImportMethods (IEnumerable<ITaskItem> libraries)
 			primary.Members.Add (method);
 			foreach (var assemblyPath in libraries) {
 				using (var pe = new PEReader (File.OpenRead (assemblyPath.ItemSpec))) {
+					if (!pe.HasMetadata) {
+						Log.LogDebugMessage ($"Skipping non-.NET assembly: {assemblyPath.ItemSpec}");
+						continue;
+					}
 					var reader = pe.GetMetadataReader ();
 					var resourceDesignerName = GetResourceDesignerClass (reader);
 					if (string.IsNullOrEmpty (resourceDesignerName)) {