Add msbuild property to disable di generation

src/Microsoft.AspNetCore.SystemWebAdapters.Analyzers.CSharp/FrameworkDependencyInjectionGenerator.cs

@@ -1,3 +1,4 @@
+using System;
 using System.CodeDom.Compiler;
 using System.Collections.Generic;
 using System.IO;
@@ -29,15 +30,27 @@ public class FrameworkDependencyInjectionGenerator : IIncrementalGenerator
 {
     public void Initialize(IncrementalGeneratorInitializationContext context)
     {
+        var options = context.AnalyzerConfigOptionsProvider
+            .Select((c, _) =>
+                c.GlobalOptions.TryGetValue("build_property.EnableSystemWebDependencyInjectionGenerator", out var enableSwitch) && enableSwitch.Equals("true", StringComparison.OrdinalIgnoreCase));
+
         var usedFrameworks = context.CompilationProvider.Select((compilation, token) => new FrameworksUsed
         {
             HttpApplicationHost = compilation.GetTypeByMetadataName("Microsoft.AspNetCore.SystemWebAdapters.Hosting.IDependencyRegistrar") is { },
             WebApi = compilation.GetTypeByMetadataName("System.Web.Http.Dependencies.IDependencyResolver") is { },
             Mvc = compilation.GetTypeByMetadataName("System.Web.Mvc.IDependencyResolver") is { },
         });
 
-        context.RegisterSourceOutput(usedFrameworks, (context, frameworks) =>
+        context.RegisterSourceOutput(usedFrameworks.Combine(options), (context, repoContext) =>
         {
+            var frameworks = repoContext.Left;
+            var isEnabled = repoContext.Right;
+
+            if (!isEnabled)
+            {
+                return;
+            }
+
             // No need to do anything if they're not referencing SystemWebAdapters with the ASP.NET Framework hosting infrastructure
             if (!frameworks.HttpApplicationHost)
             {

src/Microsoft.AspNetCore.SystemWebAdapters/build/DependencyInjectionGenerator.targets

@@ -0,0 +1,8 @@
+<Project>
+  <PropertyGroup>
+    <EnableSystemWebDependencyInjectionGenerator Condition=" '$(EnableSystemWebDependencyInjectionGenerator)' == '' ">true</EnableSystemWebDependencyInjectionGenerator>
+  </PropertyGroup>
+  <ItemGroup>
+    <CompilerVisibleProperty Include="EnableSystemWebDependencyInjectionGenerator" />
+  </ItemGroup>
+</Project>

src/Microsoft.AspNetCore.SystemWebAdapters/build/Microsoft.AspNetCore.SystemWebAdapters.targets

@@ -1,3 +1,4 @@
 <Project>
   <Import Project="$(MSBuildThisFileDirectory)NuGetContentFiles.targets"/>
+  <Import Project="$(MSBuildThisFileDirectory)DependencyInjectionGenerator.targets"/>
 </Project>