From 89a7406f5ccdbce1568d018c849a61612181b8d8 Mon Sep 17 00:00:00 2001
From: "Milko Venkov (INFRAGISTICS INC)" <b-mvenkov@microsoft.com>
Date: Tue, 30 Jun 2026 11:22:12 +0300
Subject: [PATCH 1/2] Filter re-resolved analyzers from the WPF temporary
 project

GenerateTemporaryTargetAssembly builds a temporary *_wpftmp project to resolve local types referenced from XAML. That temporary project re-runs analyzer resolution and re-adds package analyzers the parent project had intentionally removed, without honoring the packages' removal targets. In the Visual Studio in-process build this may reintroduces unnecessary analyzers and to fail.

Tag the analyzers flowed from the parent project with pfTempProjectAnalyzers metadata and set _WpfTempProjectIncludesPackageReferences on the temporary project. A new FilterTemporaryAssemblyAnalyzers target then removes any analyzer lacking that marker, restoring the authoritative analyzer set the parent project already resolved.

Fixes #9660
---
 .../Microsoft.WinFX.targets                   | 21 +++++++++++++++++++
 .../GenerateTemporaryTargetAssembly.cs        | 14 +++++++++++--
 2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/src/Microsoft.DotNet.Wpf/src/PresentationBuildTasks/Microsoft.WinFX.targets b/src/Microsoft.DotNet.Wpf/src/PresentationBuildTasks/Microsoft.WinFX.targets
index d3c9ba6d6eb..144f42c0100 100644
--- a/src/Microsoft.DotNet.Wpf/src/PresentationBuildTasks/Microsoft.WinFX.targets
+++ b/src/Microsoft.DotNet.Wpf/src/PresentationBuildTasks/Microsoft.WinFX.targets
@@ -503,6 +503,27 @@
     </ItemGroup>
   </Target>
 
+  <!--
+    ================================================================
+                                   FilterTemporaryAssemblyAnalyzers
+    ================================================================
+
+        Name : FilterTemporaryAssemblyAnalyzers
+
+        This target runs only inside the temporary project, where it drops analyzers re-resolved on their own
+         (those lacking the parent's WpfTempProjectAnalyzers marker), keeping only the set flowed from the parent.
+
+        Condition: _WpfTempProjectIncludesPackageReferences == true
+  -->
+  <Target Name="FilterTemporaryAssemblyAnalyzers"
+          AfterTargets="RemoveDuplicateAnalyzers"
+          BeforeTargets="CoreCompile"
+          Condition="'$(_WpfTempProjectIncludesPackageReferences)' == 'true'">
+    <ItemGroup>
+        <Analyzer Remove="@(Analyzer)" Condition="'%(Analyzer.WpfTempProjectAnalyzers)' != 'true'" />
+    </ItemGroup>
+  </Target>
+
 <!--
     ================================================================
                                    SatelliteOnlyMarkupCompilePass2
diff --git a/src/Microsoft.DotNet.Wpf/src/PresentationBuildTasks/Microsoft/Build/Tasks/Windows/GenerateTemporaryTargetAssembly.cs b/src/Microsoft.DotNet.Wpf/src/PresentationBuildTasks/Microsoft/Build/Tasks/Windows/GenerateTemporaryTargetAssembly.cs
index 812f9116dbc..b2be838de64 100644
--- a/src/Microsoft.DotNet.Wpf/src/PresentationBuildTasks/Microsoft/Build/Tasks/Windows/GenerateTemporaryTargetAssembly.cs
+++ b/src/Microsoft.DotNet.Wpf/src/PresentationBuildTasks/Microsoft/Build/Tasks/Windows/GenerateTemporaryTargetAssembly.cs
@@ -262,7 +262,7 @@ private bool ExecuteGenerateTemporaryTargetAssemblyWithPackageReferenceSupport()
                 AddNewItems(xmlProjectDoc, CompileTypeName, GeneratedCodeFiles);
 
                 // Add Analyzers to Analyzer item list.
-                AddNewItems(xmlProjectDoc, AnalyzerTypeName, Analyzers);
+                AddNewItems(xmlProjectDoc, AnalyzerTypeName, Analyzers, true);
 
                 // Replace implicit SDK imports with explicit SDK imports
                 ReplaceImplicitImports(xmlProjectDoc);
@@ -275,6 +275,7 @@ private bool ExecuteGenerateTemporaryTargetAssemblyWithPackageReferenceSupport()
                     ( nameof(BaseIntermediateOutputPath), BaseIntermediateOutputPath ),
                     ( nameof(MSBuildProjectExtensionsPath), MSBuildProjectExtensionsPath ),
                     ( "_TargetAssemblyProjectName", Path.GetFileNameWithoutExtension(CurrentProject) ),
+                    ( "_WpfTempProjectIncludesPackageReferences", "true" ),
                     ( nameof(RootNamespace), RootNamespace ),
                 };
 
@@ -694,7 +695,7 @@ private void RemovePropertiesByName(XmlDocument xmlProjectDoc, string sPropertyN
         //
         // Add a list of files into an Item in the project file, the ItemName is specified by sItemName.
         //
-        private void AddNewItems(XmlDocument xmlProjectDoc, string sItemName, ITaskItem[] pItemList)
+        private void AddNewItems(XmlDocument xmlProjectDoc, string sItemName, ITaskItem[] pItemList, bool tagWpfTempProjectAnalyzers = false)
         {
             if (xmlProjectDoc == null || String.IsNullOrEmpty(sItemName) || pItemList == null)
             {
@@ -744,6 +745,13 @@ private void AddNewItems(XmlDocument xmlProjectDoc, string sItemName, ITaskItem[
                     nodeItem.AppendChild(embedItem);
                 }
 
+                if (tagWpfTempProjectAnalyzers)
+                {
+                    XmlElement metadataItem = xmlProjectDoc.CreateElement(WPFTEMPPROJECTANALYZERS, root.NamespaceURI);
+                    metadataItem.InnerText = "true";
+                    nodeItem.AppendChild(metadataItem);
+                }
+
                 // Add current item node into the children list of ItemGroup
                 nodeItemGroup.AppendChild(nodeItem);
             }
@@ -936,6 +944,8 @@ private static XmlNode CreateImportProjectSdkNode(XmlDocument xmlProjectDoc, str
 
         private const string WPFTMP = "wpftmp";
 
+        private const string WPFTEMPPROJECTANALYZERS = "WpfTempProjectAnalyzers";
+
         private static readonly char[] s_semicolonChar = [';'];
 
         #endregion Private Fields

From 8a1ed0c80e7f679133b7af47da42495cf4c5963a Mon Sep 17 00:00:00 2001
From: "Milko Venkov (INFRAGISTICS INC)" <b-mvenkov@microsoft.com>
Date: Wed, 1 Jul 2026 13:12:59 +0300
Subject: [PATCH 2/2] Address PR comments

---
 .../src/PresentationBuildTasks/Microsoft.WinFX.targets         | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/Microsoft.DotNet.Wpf/src/PresentationBuildTasks/Microsoft.WinFX.targets b/src/Microsoft.DotNet.Wpf/src/PresentationBuildTasks/Microsoft.WinFX.targets
index 144f42c0100..f6f5aa40227 100644
--- a/src/Microsoft.DotNet.Wpf/src/PresentationBuildTasks/Microsoft.WinFX.targets
+++ b/src/Microsoft.DotNet.Wpf/src/PresentationBuildTasks/Microsoft.WinFX.targets
@@ -516,8 +516,7 @@
         Condition: _WpfTempProjectIncludesPackageReferences == true
   -->
   <Target Name="FilterTemporaryAssemblyAnalyzers"
-          AfterTargets="RemoveDuplicateAnalyzers"
-          BeforeTargets="CoreCompile"
+          BeforeTargets="RemoveDuplicateAnalyzers;CoreCompile"
           Condition="'$(_WpfTempProjectIncludesPackageReferences)' == 'true'">
     <ItemGroup>
         <Analyzer Remove="@(Analyzer)" Condition="'%(Analyzer.WpfTempProjectAnalyzers)' != 'true'" />