From a8eaca62489763d4538007d8b249a6932aeb7a35 Mon Sep 17 00:00:00 2001
From: Martin Costello <martin@martincostello.com>
Date: Tue, 12 Nov 2024 19:36:23 +0000
Subject: [PATCH] Support .NET 9 (#3007)

* Support .NET 9

- Add `net9.0` TFMs.
- Drop TFMs for all out-of-support versions of .NET.
- Bump version to `7.0.0`.
- Only audit direct NuGet dependencies.
- Suppress vulnerabilities in IdentityServer4 used in sample.
- Remove some now-redundant pre-processor directives.

* Update package references

Target .NET 9 versions for Microsoft.AspNetCore.OpenApi in test sites.

* Bump Microsoft.OpenApi

Bump Microsoft.OpenApi to the latest version.

* Update .NET SDK to 9.0.100-preview.7.24407.12 (#3025)

* Update .NET SDK

Update .NET SDK to version 9.0.100-preview.7.24407.12.

---
updated-dependencies:
- dependency-name: Microsoft.NET.Sdk
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

* Update NuGet packages
Bump NuGet packages for .NET 9 preview 7.

---------

Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Martin Costello <martin@martincostello.com>

* Bump Microsoft.OpenApi

Bump Microsoft.OpenApi to 1.6.18.

* Bump Microsoft.OpenApi

Bump Microsoft.OpenApi to 1.6.20.

* Bump Microsoft.OpenApi

Update Microsoft.OpenApi to 1.6.21.

* Update .NET SDK to 9.0.100-rc.1.24452.12 (#3066)

* Update .NET SDK

Update .NET SDK to version 9.0.100-rc.1.24452.12.

---
updated-dependencies:
- dependency-name: Microsoft.NET.Sdk
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

* Update NuGet packages
Update NuGet packages for RC1.

---------

Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Martin Costello <martin@martincostello.com>

* Make middlewares internal

Make all the middleware classes internal as they have no useful public-facing functionality (e.g. virtual members).

Resolves #2805.

* Update .NET SDK to 9.0.100-rc.2.24474.11 (#3098)

* Update .NET SDK

Update .NET SDK to version 9.0.100-rc.2.24474.11.

---
updated-dependencies:
- dependency-name: Microsoft.NET.Sdk
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

* Update NuGet packages
Update NuGet packages for .NET 9 RC2.

---------

Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Martin Costello <martin@martincostello.com>

* Bump Microsoft.OpenApi

Bump Microsoft.OpenApi to 1.6.22.

* Bump packages

Update packages for ASP.NET Core 8.0.10.

* Swap order of TFMs

Put the newest first so Visual Studio loads the latest version as the selected TFM by default.

* Apply suggestions from code review

- Remove redundant comment.
- Add link to tracking issue in comment.

* Add [ActivatorUtilitiesConstructor]

React to aspnet/Announcements#514 for .NET 9.

* Update to .NET 9 GA
Update to the stable version of .NET 9.

* Bump .NET 8 packages

Bump test packages for .NET 8.

---------

Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
---
 .github/workflows/build.yml                   |   2 +-
 Directory.Build.props                         |  12 +-
 Directory.Packages.props                      |   4 +-
 global.json                                   |   2 +-
 .../Swashbuckle.AspNetCore.Annotations.csproj |   2 +-
 ...hbuckle.AspNetCore.ApiTesting.Xunit.csproj |   2 +-
 .../Swashbuckle.AspNetCore.ApiTesting.csproj  |  20 +--
 .../CommandRunner.cs                          |   2 +-
 .../HostingApplication.cs                     |   6 -
 src/Swashbuckle.AspNetCore.Cli/Program.cs     |   2 +-
 .../Swashbuckle.AspNetCore.Cli.csproj         |   6 +-
 .../Swashbuckle.AspNetCore.Newtonsoft.csproj  |  18 +--
 .../.NETCoreApp/PublicAPI.Shipped.txt         |   1 -
 .../.NETCoreApp/PublicAPI.Unshipped.txt       |   0
 .../.NETStandard/PublicAPI.Shipped.txt        |   1 -
 .../.NETStandard/PublicAPI.Unshipped.txt      |   0
 .../PublicAPI/PublicAPI.Shipped.txt           |   2 -
 .../ReDocMiddleware.cs                        |   2 +-
 .../Swashbuckle.AspNetCore.ReDoc.csproj       |   2 +-
 .../.NETCoreApp/PublicAPI.Shipped.txt         |   1 -
 .../PublicAPI/PublicAPI.Shipped.txt           |   3 -
 .../SwaggerMiddleware.cs                      |   3 +-
 .../Swashbuckle.AspNetCore.Swagger.csproj     |   2 +-
 .../ConfigureSwaggerGeneratorOptions.cs       |   2 +-
 .../SchemaGenerator/SchemaGenerator.cs        |   2 +-
 .../ApiParameterDescriptionExtensions.cs      |   4 +-
 .../Swashbuckle.AspNetCore.SwaggerGen.csproj  |   2 +-
 .../.NETCoreApp/PublicAPI.Shipped.txt         |   1 -
 .../.NETCoreApp/PublicAPI.Unshipped.txt       |   0
 .../.NETStandard/PublicAPI.Shipped.txt        |   1 -
 .../.NETStandard/PublicAPI.Unshipped.txt      |   0
 .../PublicAPI/PublicAPI.Shipped.txt           |   2 -
 .../SwaggerUIBuilderExtensions.cs             |   2 +-
 .../SwaggerUIMiddleware.cs                    |   4 +-
 .../Swashbuckle.AspNetCore.SwaggerUI.csproj   |   2 +-
 .../Swashbuckle.AspNetCore.csproj             |  10 +-
 ...hbuckle.AspNetCore.Annotations.Test.csproj |   2 +-
 ...shbuckle.AspNetCore.ApiTesting.Test.csproj |   2 +-
 .../Swashbuckle.AspNetCore.Cli.Test.csproj    |   2 +-
 ...hbuckle.AspNetCore.IntegrationTests.csproj |  11 +-
 ...shbuckle.AspNetCore.Newtonsoft.Test.csproj |   2 +-
 ...shbuckle.AspNetCore.SwaggerGen.Test.csproj |   2 +-
 .../ApiExplorer/ApiDescriptionFactory.cs      |   4 -
 .../Swashbuckle.AspNetCore.TestSupport.csproj |   2 +-
 test/WebSites/Basic/Basic.csproj              |   2 +-
 test/WebSites/CliExample/CliExample.csproj    |   2 +-
 .../wwwroot/swagger/v1/swagger_net9.0.json    |  54 +++++++
 .../CliExampleWithFactory.csproj              |   2 +-
 .../wwwroot/swagger/v1/swagger_net9.0.json    |  54 +++++++
 .../ConfigFromFile/ConfigFromFile.csproj      |   2 +-
 .../CustomDocumentSerializer.csproj           |   2 +-
 .../CustomUIConfig/CustomUIConfig.csproj      |   2 +-
 .../CustomUIIndex/CustomUIIndex.csproj        |   2 +-
 .../GenericControllers.csproj                 |   2 +-
 test/WebSites/MinimalApp/MinimalApp.csproj    |   2 +-
 .../MinimalAppWithHostedServices.csproj       |   2 +-
 .../MultipleVersions/MultipleVersions.csproj  |   2 +-
 .../MvcWithNullable/MvcWithNullable.csproj    |   6 +-
 .../NswagClientExample.csproj                 |   2 +-
 .../NswagClientExample/swagger_net9.0.json    | 140 ++++++++++++++++++
 .../OAuth2Integration.csproj                  |  11 +-
 test/WebSites/ReDoc/ReDoc.csproj              |   2 +-
 .../TestFirst.IntegrationTests.csproj         |   2 +-
 test/WebSites/TestFirst/TestFirst.csproj      |   2 +-
 .../TopLevelSwaggerDoc.csproj                 |   2 +-
 test/WebSites/WebApi.Aot/WebApi.Aot.csproj    |   2 +-
 test/WebSites/WebApi/WebApi.csproj            |   6 +-
 67 files changed, 346 insertions(+), 113 deletions(-)
 delete mode 100644 src/Swashbuckle.AspNetCore.ReDoc/PublicAPI/.NETCoreApp/PublicAPI.Shipped.txt
 delete mode 100644 src/Swashbuckle.AspNetCore.ReDoc/PublicAPI/.NETCoreApp/PublicAPI.Unshipped.txt
 delete mode 100644 src/Swashbuckle.AspNetCore.ReDoc/PublicAPI/.NETStandard/PublicAPI.Shipped.txt
 delete mode 100644 src/Swashbuckle.AspNetCore.ReDoc/PublicAPI/.NETStandard/PublicAPI.Unshipped.txt
 delete mode 100644 src/Swashbuckle.AspNetCore.SwaggerUI/PublicAPI/.NETCoreApp/PublicAPI.Shipped.txt
 delete mode 100644 src/Swashbuckle.AspNetCore.SwaggerUI/PublicAPI/.NETCoreApp/PublicAPI.Unshipped.txt
 delete mode 100644 src/Swashbuckle.AspNetCore.SwaggerUI/PublicAPI/.NETStandard/PublicAPI.Shipped.txt
 delete mode 100644 src/Swashbuckle.AspNetCore.SwaggerUI/PublicAPI/.NETStandard/PublicAPI.Unshipped.txt
 create mode 100644 test/WebSites/CliExample/wwwroot/swagger/v1/swagger_net9.0.json
 create mode 100644 test/WebSites/CliExampleWithFactory/wwwroot/swagger/v1/swagger_net9.0.json
 create mode 100644 test/WebSites/NswagClientExample/swagger_net9.0.json

diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index c376eca45a..022e9d3142 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -52,7 +52,7 @@ jobs:
       with:
         dotnet-version: |
           6.0.x
-          7.0.x
+          8.0.x
 
     - name: Setup .NET SDK
       uses: actions/setup-dotnet@3e891b0cb619bf60e2c25674b222b8940e2c1c25 # v4.1.0
diff --git a/Directory.Build.props b/Directory.Build.props
index a815c00f0d..0d83b78f80 100644
--- a/Directory.Build.props
+++ b/Directory.Build.props
@@ -20,18 +20,10 @@
     <ManagePackageVersionsCentrally>true</ManagePackageVersionsCentrally>
     <NeutralLanguage>en-US</NeutralLanguage>
     <!--
-    TODO Remove deprecated TFMs
-    -->
-    <CheckEolTargetFramework>false</CheckEolTargetFramework>
-    <NoWarn>$(NoWarn);NETSDK1138</NoWarn>
-    <!--
-    TODO Update packages to resolve vulnerability warnings
-    -->
-    <NoWarn>$(NoWarn);NU1902;NU1903</NoWarn>
-    <!--
     TODO Fix warning from Swashbuckle.AspNetCore with dotnet pack
     -->
     <NoWarn>$(NoWarn);NU5128</NoWarn>
+    <NuGetAuditMode>direct</NuGetAuditMode>
     <!--
     TODO Go through the code and add nullable annotations
     <Nullable>enable</Nullable>
@@ -49,7 +41,7 @@
     <SymbolPackageFormat>snupkg</SymbolPackageFormat>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
     <UseArtifactsOutput>true</UseArtifactsOutput>
-    <VersionPrefix>6.9.1</VersionPrefix>
+    <VersionPrefix>7.0.0</VersionPrefix>
     <WarnOnPackingNonPackableProject>false</WarnOnPackingNonPackableProject>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(GITHUB_ACTIONS)' != '' ">
diff --git a/Directory.Packages.props b/Directory.Packages.props
index 1e60a82420..b6e6834f7a 100644
--- a/Directory.Packages.props
+++ b/Directory.Packages.props
@@ -21,8 +21,8 @@
     <PackageVersion Include="Microsoft.AspNetCore.TestHost" Version="6.0.32" />
     <PackageVersion Include="Microsoft.CodeAnalysis.PublicApiAnalyzers" Version="3.3.4" />
     <PackageVersion Include="Microsoft.Extensions.FileProviders.Embedded" Version="2.1.0" />
-    <PackageVersion Include="Microsoft.OpenApi" Version="1.6.14" />
-    <PackageVersion Include="Microsoft.OpenApi.Readers" Version="1.6.14" />
+    <PackageVersion Include="Microsoft.OpenApi" Version="1.6.22" />
+    <PackageVersion Include="Microsoft.OpenApi.Readers" Version="1.6.22" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.10.0" />
     <PackageVersion Include="Newtonsoft.Json" Version="13.0.3" />
     <PackageVersion Include="NSubstitute" Version="5.1.0" />
diff --git a/global.json b/global.json
index 66e4c11e7c..217f7c9fb3 100644
--- a/global.json
+++ b/global.json
@@ -1,6 +1,6 @@
 {
   "sdk": {
-    "version": "8.0.403",
+    "version": "9.0.100",
     "allowPrerelease": false,
     "rollForward": "latestMajor"
   }
diff --git a/src/Swashbuckle.AspNetCore.Annotations/Swashbuckle.AspNetCore.Annotations.csproj b/src/Swashbuckle.AspNetCore.Annotations/Swashbuckle.AspNetCore.Annotations.csproj
index 80765f99f3..c5ae6716cd 100644
--- a/src/Swashbuckle.AspNetCore.Annotations/Swashbuckle.AspNetCore.Annotations.csproj
+++ b/src/Swashbuckle.AspNetCore.Annotations/Swashbuckle.AspNetCore.Annotations.csproj
@@ -8,7 +8,7 @@
     <NoWarn>$(NoWarn);1591</NoWarn>
     <PackageTags>swagger;documentation;discovery;help;webapi;aspnet;aspnetcore;annotations</PackageTags>
     <SignAssembly>true</SignAssembly>
-    <TargetFrameworks>netstandard2.0;netcoreapp3.0;net5.0;net6.0;net7.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0;netstandard2.0</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/src/Swashbuckle.AspNetCore.ApiTesting.Xunit/Swashbuckle.AspNetCore.ApiTesting.Xunit.csproj b/src/Swashbuckle.AspNetCore.ApiTesting.Xunit/Swashbuckle.AspNetCore.ApiTesting.Xunit.csproj
index b20ff1cfa4..46c4f17b3e 100644
--- a/src/Swashbuckle.AspNetCore.ApiTesting.Xunit/Swashbuckle.AspNetCore.ApiTesting.Xunit.csproj
+++ b/src/Swashbuckle.AspNetCore.ApiTesting.Xunit/Swashbuckle.AspNetCore.ApiTesting.Xunit.csproj
@@ -7,7 +7,7 @@
     <IsTestProject>false</IsTestProject>
     <NoWarn>$(NoWarn);1591</NoWarn>
     <PackageTags>swagger;openapi;test-first;spec-first;testing;aspnetcore;xunit</PackageTags>
-    <TargetFrameworks>netstandard2.0;netcoreapp3.0;net5.0;net6.0;net7.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0;netstandard2.0</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/src/Swashbuckle.AspNetCore.ApiTesting/Swashbuckle.AspNetCore.ApiTesting.csproj b/src/Swashbuckle.AspNetCore.ApiTesting/Swashbuckle.AspNetCore.ApiTesting.csproj
index dc86ee5cc5..2ecfdab0ff 100644
--- a/src/Swashbuckle.AspNetCore.ApiTesting/Swashbuckle.AspNetCore.ApiTesting.csproj
+++ b/src/Swashbuckle.AspNetCore.ApiTesting/Swashbuckle.AspNetCore.ApiTesting.csproj
@@ -6,7 +6,7 @@
     <IsPackable>true</IsPackable>
     <NoWarn>$(NoWarn);1591</NoWarn>
     <PackageTags>swagger;openapi;test-first;spec-first;testing;aspnetcore</PackageTags>
-    <TargetFrameworks>netstandard2.0;netcoreapp3.0;net5.0;net6.0;net7.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0;netstandard2.0</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>
@@ -16,29 +16,21 @@
   </ItemGroup>
 
   <ItemGroup Condition=" '$(TargetFramework)' == 'netstandard2.0' ">
-    <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" VersionOverride="2.1.2" />
-  </ItemGroup>
-
-  <ItemGroup Condition=" '$(TargetFramework)' == 'netcoreapp3.0' ">
-    <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" VersionOverride="3.0.0" />
-  </ItemGroup>
-
-  <ItemGroup Condition=" '$(TargetFramework)' == 'net5.0' ">
-    <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" VersionOverride="5.0.0" />
+    <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" VersionOverride="2.1.3" />
   </ItemGroup>
 
   <ItemGroup Condition=" '$(TargetFramework)' == 'net6.0' ">
     <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" VersionOverride="6.0.0" />
   </ItemGroup>
 
-  <ItemGroup Condition=" '$(TargetFramework)' == 'net7.0' ">
-    <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" VersionOverride="7.0.0" />
-  </ItemGroup>
-
   <ItemGroup Condition=" '$(TargetFramework)' == 'net8.0' ">
     <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" VersionOverride="8.0.0" />
   </ItemGroup>
 
+  <ItemGroup Condition=" '$(TargetFramework)' == 'net9.0' ">
+    <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" VersionOverride="9.0.0" />
+  </ItemGroup>
+
   <ItemGroup>
     <PackageReference Include="Microsoft.CodeAnalysis.PublicApiAnalyzers" PrivateAssets="All" />
     <AdditionalFiles Include="PublicAPI\PublicAPI.Shipped.txt" />
diff --git a/src/Swashbuckle.AspNetCore.Cli/CommandRunner.cs b/src/Swashbuckle.AspNetCore.Cli/CommandRunner.cs
index 3bccca13b4..6eccd7874a 100644
--- a/src/Swashbuckle.AspNetCore.Cli/CommandRunner.cs
+++ b/src/Swashbuckle.AspNetCore.Cli/CommandRunner.cs
@@ -5,7 +5,7 @@
 
 namespace Swashbuckle.AspNetCore.Cli
 {
-    public class CommandRunner
+    internal class CommandRunner
     {
         private readonly Dictionary<string, string> _argumentDescriptors;
         private readonly Dictionary<string, OptionDescriptor> _optionDescriptors;
diff --git a/src/Swashbuckle.AspNetCore.Cli/HostingApplication.cs b/src/Swashbuckle.AspNetCore.Cli/HostingApplication.cs
index 3c7685c088..4dfe6680d5 100644
--- a/src/Swashbuckle.AspNetCore.Cli/HostingApplication.cs
+++ b/src/Swashbuckle.AspNetCore.Cli/HostingApplication.cs
@@ -4,9 +4,7 @@
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Hosting.Server;
 using Microsoft.AspNetCore.Http.Features;
-#if NETCOREAPP3_0_OR_GREATER
 using Microsoft.Extensions.DependencyInjection;
-#endif
 using Microsoft.Extensions.Hosting;
 
 namespace Swashbuckle.AspNetCore.Cli
@@ -19,9 +17,6 @@ internal class HostingApplication
     {
         internal static IServiceProvider GetServiceProvider(Assembly assembly)
         {
-#if NETCOREAPP2_1
-            return null;
-#else
             // We're disabling the default server and the console host lifetime. This will disable:
             // 1. Listening on ports
             // 2. Logging to the console from the default host.
@@ -102,7 +97,6 @@ void OnEntryPointExit(Exception exception)
             }
 
             return null;
-#endif
         }
 
         private class NoopHostLifetime : IHostLifetime
diff --git a/src/Swashbuckle.AspNetCore.Cli/Program.cs b/src/Swashbuckle.AspNetCore.Cli/Program.cs
index 9b06fc9e84..62dfadffb4 100644
--- a/src/Swashbuckle.AspNetCore.Cli/Program.cs
+++ b/src/Swashbuckle.AspNetCore.Cli/Program.cs
@@ -15,7 +15,7 @@
 
 namespace Swashbuckle.AspNetCore.Cli
 {
-    public class Program
+    internal class Program
     {
         public static int Main(string[] args)
         {
diff --git a/src/Swashbuckle.AspNetCore.Cli/Swashbuckle.AspNetCore.Cli.csproj b/src/Swashbuckle.AspNetCore.Cli/Swashbuckle.AspNetCore.Cli.csproj
index 26c75da3cb..0a97878a03 100644
--- a/src/Swashbuckle.AspNetCore.Cli/Swashbuckle.AspNetCore.Cli.csproj
+++ b/src/Swashbuckle.AspNetCore.Cli/Swashbuckle.AspNetCore.Cli.csproj
@@ -7,7 +7,7 @@
     <OutputType>Exe</OutputType>
     <PackAsTool>true</PackAsTool>
     <PackageId>Swashbuckle.AspNetCore.Cli</PackageId>
-    <TargetFrameworks>netcoreapp2.1;netcoreapp3.0;net5.0;net6.0;net7.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0</TargetFrameworks>
     <ToolCommandName>swagger</ToolCommandName>
   </PropertyGroup>
 
@@ -15,8 +15,8 @@
     <ProjectReference Include="..\Swashbuckle.AspNetCore.Swagger\Swashbuckle.AspNetCore.Swagger.csproj" />
   </ItemGroup>
 
-  <ItemGroup Condition=" '$(TargetFramework)' == 'netcoreapp2.1' ">
-    <PackageReference Include="Microsoft.AspNetCore" />
+  <ItemGroup>
+    <InternalsVisibleTo Include="Swashbuckle.AspNetCore.Cli.Test" />
   </ItemGroup>
 
 </Project>
diff --git a/src/Swashbuckle.AspNetCore.Newtonsoft/Swashbuckle.AspNetCore.Newtonsoft.csproj b/src/Swashbuckle.AspNetCore.Newtonsoft/Swashbuckle.AspNetCore.Newtonsoft.csproj
index 13fd76f336..a1b44793d4 100644
--- a/src/Swashbuckle.AspNetCore.Newtonsoft/Swashbuckle.AspNetCore.Newtonsoft.csproj
+++ b/src/Swashbuckle.AspNetCore.Newtonsoft/Swashbuckle.AspNetCore.Newtonsoft.csproj
@@ -6,7 +6,7 @@
     <IsPackable>true</IsPackable>
     <PackageTags>swagger;documentation;discovery;help;webapi;aspnet;aspnetcore;newtonsoft</PackageTags>
     <SignAssembly>true</SignAssembly>
-    <TargetFrameworks>netstandard2.0;netcoreapp3.0;net5.0;net6.0;net7.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0;netstandard2.0</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>
@@ -17,26 +17,18 @@
     <PackageReference Include="Microsoft.AspNetCore.Mvc.Formatters.Json" />
   </ItemGroup>
 
-  <ItemGroup Condition=" '$(TargetFramework)' == 'netcoreapp3.0' ">
-    <PackageReference Include="Microsoft.AspNetCore.Mvc.NewtonsoftJson" VersionOverride="3.0.0" />
-  </ItemGroup>
-
-  <ItemGroup Condition=" '$(TargetFramework)' == 'net5.0' ">
-    <PackageReference Include="Microsoft.AspNetCore.Mvc.NewtonsoftJson" VersionOverride="5.0.0" />
-  </ItemGroup>
-
   <ItemGroup Condition=" '$(TargetFramework)' == 'net6.0' ">
     <PackageReference Include="Microsoft.AspNetCore.Mvc.NewtonsoftJson" VersionOverride="6.0.0" />
   </ItemGroup>
 
-   <ItemGroup Condition=" '$(TargetFramework)' == 'net7.0' ">
-    <PackageReference Include="Microsoft.AspNetCore.Mvc.NewtonsoftJson" VersionOverride="7.0.0" />
-  </ItemGroup>
-
   <ItemGroup Condition=" '$(TargetFramework)' == 'net8.0' ">
     <PackageReference Include="Microsoft.AspNetCore.Mvc.NewtonsoftJson" VersionOverride="8.0.0" />
   </ItemGroup>
 
+  <ItemGroup Condition=" '$(TargetFramework)' == 'net9.0' ">
+    <PackageReference Include="Microsoft.AspNetCore.Mvc.NewtonsoftJson" VersionOverride="9.0.0" />
+  </ItemGroup>
+
   <ItemGroup>
     <PackageReference Include="Microsoft.CodeAnalysis.PublicApiAnalyzers" PrivateAssets="All" />
     <AdditionalFiles Include="PublicAPI\PublicAPI.Shipped.txt" />
diff --git a/src/Swashbuckle.AspNetCore.ReDoc/PublicAPI/.NETCoreApp/PublicAPI.Shipped.txt b/src/Swashbuckle.AspNetCore.ReDoc/PublicAPI/.NETCoreApp/PublicAPI.Shipped.txt
deleted file mode 100644
index 8e15f9fdb3..0000000000
--- a/src/Swashbuckle.AspNetCore.ReDoc/PublicAPI/.NETCoreApp/PublicAPI.Shipped.txt
+++ /dev/null
@@ -1 +0,0 @@
-Swashbuckle.AspNetCore.ReDoc.ReDocMiddleware.ReDocMiddleware(Microsoft.AspNetCore.Http.RequestDelegate next, Microsoft.AspNetCore.Hosting.IWebHostEnvironment hostingEnv, Microsoft.Extensions.Logging.ILoggerFactory loggerFactory, Swashbuckle.AspNetCore.ReDoc.ReDocOptions options) -> void
diff --git a/src/Swashbuckle.AspNetCore.ReDoc/PublicAPI/.NETCoreApp/PublicAPI.Unshipped.txt b/src/Swashbuckle.AspNetCore.ReDoc/PublicAPI/.NETCoreApp/PublicAPI.Unshipped.txt
deleted file mode 100644
index e69de29bb2..0000000000
diff --git a/src/Swashbuckle.AspNetCore.ReDoc/PublicAPI/.NETStandard/PublicAPI.Shipped.txt b/src/Swashbuckle.AspNetCore.ReDoc/PublicAPI/.NETStandard/PublicAPI.Shipped.txt
deleted file mode 100644
index 62be68d0ae..0000000000
--- a/src/Swashbuckle.AspNetCore.ReDoc/PublicAPI/.NETStandard/PublicAPI.Shipped.txt
+++ /dev/null
@@ -1 +0,0 @@
-Swashbuckle.AspNetCore.ReDoc.ReDocMiddleware.ReDocMiddleware(Microsoft.AspNetCore.Http.RequestDelegate next, Microsoft.AspNetCore.Hosting.IHostingEnvironment hostingEnv, Microsoft.Extensions.Logging.ILoggerFactory loggerFactory, Swashbuckle.AspNetCore.ReDoc.ReDocOptions options) -> void
diff --git a/src/Swashbuckle.AspNetCore.ReDoc/PublicAPI/.NETStandard/PublicAPI.Unshipped.txt b/src/Swashbuckle.AspNetCore.ReDoc/PublicAPI/.NETStandard/PublicAPI.Unshipped.txt
deleted file mode 100644
index e69de29bb2..0000000000
diff --git a/src/Swashbuckle.AspNetCore.ReDoc/PublicAPI/PublicAPI.Shipped.txt b/src/Swashbuckle.AspNetCore.ReDoc/PublicAPI/PublicAPI.Shipped.txt
index 13e69c69d1..fcd2184d8a 100644
--- a/src/Swashbuckle.AspNetCore.ReDoc/PublicAPI/PublicAPI.Shipped.txt
+++ b/src/Swashbuckle.AspNetCore.ReDoc/PublicAPI/PublicAPI.Shipped.txt
@@ -47,8 +47,6 @@ Swashbuckle.AspNetCore.ReDoc.ConfigObject.SortPropsAlphabetically.get -> bool
 Swashbuckle.AspNetCore.ReDoc.ConfigObject.SortPropsAlphabetically.set -> void
 Swashbuckle.AspNetCore.ReDoc.ConfigObject.UntrustedSpec.get -> bool
 Swashbuckle.AspNetCore.ReDoc.ConfigObject.UntrustedSpec.set -> void
-Swashbuckle.AspNetCore.ReDoc.ReDocMiddleware
-Swashbuckle.AspNetCore.ReDoc.ReDocMiddleware.Invoke(Microsoft.AspNetCore.Http.HttpContext httpContext) -> System.Threading.Tasks.Task
 Swashbuckle.AspNetCore.ReDoc.ReDocOptions
 Swashbuckle.AspNetCore.ReDoc.ReDocOptions.ConfigObject.get -> Swashbuckle.AspNetCore.ReDoc.ConfigObject
 Swashbuckle.AspNetCore.ReDoc.ReDocOptions.ConfigObject.set -> void
diff --git a/src/Swashbuckle.AspNetCore.ReDoc/ReDocMiddleware.cs b/src/Swashbuckle.AspNetCore.ReDoc/ReDocMiddleware.cs
index bd4ddf044e..60315dc1f6 100644
--- a/src/Swashbuckle.AspNetCore.ReDoc/ReDocMiddleware.cs
+++ b/src/Swashbuckle.AspNetCore.ReDoc/ReDocMiddleware.cs
@@ -22,7 +22,7 @@
 
 namespace Swashbuckle.AspNetCore.ReDoc
 {
-    public class ReDocMiddleware
+    internal sealed class ReDocMiddleware
     {
         private const string EmbeddedFileNamespace = "Swashbuckle.AspNetCore.ReDoc.node_modules.redoc.bundles";
 
diff --git a/src/Swashbuckle.AspNetCore.ReDoc/Swashbuckle.AspNetCore.ReDoc.csproj b/src/Swashbuckle.AspNetCore.ReDoc/Swashbuckle.AspNetCore.ReDoc.csproj
index a5157a26b3..9984ac5e3f 100644
--- a/src/Swashbuckle.AspNetCore.ReDoc/Swashbuckle.AspNetCore.ReDoc.csproj
+++ b/src/Swashbuckle.AspNetCore.ReDoc/Swashbuckle.AspNetCore.ReDoc.csproj
@@ -8,7 +8,7 @@
     <NoWarn>$(NoWarn);1591</NoWarn>
     <PackageTags>swagger;documentation;discovery;help;webapi;aspnet;aspnetcore;redoc</PackageTags>
     <SignAssembly>true</SignAssembly>
-    <TargetFrameworks>netstandard2.0;netcoreapp3.0;net5.0;net6.0;net7.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0;netstandard2.0</TargetFrameworks>
   </PropertyGroup>
   <PropertyGroup Condition="$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net8.0'))">
     <EnableAotAnalyzer>true</EnableAotAnalyzer>
diff --git a/src/Swashbuckle.AspNetCore.Swagger/PublicAPI/.NETCoreApp/PublicAPI.Shipped.txt b/src/Swashbuckle.AspNetCore.Swagger/PublicAPI/.NETCoreApp/PublicAPI.Shipped.txt
index 3339211111..7904c68055 100644
--- a/src/Swashbuckle.AspNetCore.Swagger/PublicAPI/.NETCoreApp/PublicAPI.Shipped.txt
+++ b/src/Swashbuckle.AspNetCore.Swagger/PublicAPI/.NETCoreApp/PublicAPI.Shipped.txt
@@ -1,2 +1 @@
 static Microsoft.AspNetCore.Builder.SwaggerBuilderExtensions.MapSwagger(this Microsoft.AspNetCore.Routing.IEndpointRouteBuilder endpoints, string pattern = "/swagger/{documentName}/swagger.{extension:regex(^(json|ya?ml)$)}", System.Action<Swashbuckle.AspNetCore.Swagger.SwaggerEndpointOptions> setupAction = null) -> Microsoft.AspNetCore.Builder.IEndpointConventionBuilder
-Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.SwaggerMiddleware(Microsoft.AspNetCore.Http.RequestDelegate next, Swashbuckle.AspNetCore.Swagger.SwaggerOptions options, Microsoft.AspNetCore.Routing.Template.TemplateBinderFactory templateBinderFactory) -> void
diff --git a/src/Swashbuckle.AspNetCore.Swagger/PublicAPI/PublicAPI.Shipped.txt b/src/Swashbuckle.AspNetCore.Swagger/PublicAPI/PublicAPI.Shipped.txt
index c9f143c5b2..5252affd44 100644
--- a/src/Swashbuckle.AspNetCore.Swagger/PublicAPI/PublicAPI.Shipped.txt
+++ b/src/Swashbuckle.AspNetCore.Swagger/PublicAPI/PublicAPI.Shipped.txt
@@ -16,9 +16,6 @@ Swashbuckle.AspNetCore.Swagger.SwaggerEndpointOptions.PreSerializeFilters.get ->
 Swashbuckle.AspNetCore.Swagger.SwaggerEndpointOptions.SerializeAsV2.get -> bool
 Swashbuckle.AspNetCore.Swagger.SwaggerEndpointOptions.SerializeAsV2.set -> void
 Swashbuckle.AspNetCore.Swagger.SwaggerEndpointOptions.SwaggerEndpointOptions() -> void
-Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware
-Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.Invoke(Microsoft.AspNetCore.Http.HttpContext httpContext, Swashbuckle.AspNetCore.Swagger.ISwaggerProvider swaggerProvider) -> System.Threading.Tasks.Task
-Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.SwaggerMiddleware(Microsoft.AspNetCore.Http.RequestDelegate next, Swashbuckle.AspNetCore.Swagger.SwaggerOptions options) -> void
 Swashbuckle.AspNetCore.Swagger.SwaggerOptions
 Swashbuckle.AspNetCore.Swagger.SwaggerOptions.CustomDocumentSerializer.get -> Swashbuckle.AspNetCore.Swagger.ISwaggerDocumentSerializer
 Swashbuckle.AspNetCore.Swagger.SwaggerOptions.CustomDocumentSerializer.set -> void
diff --git a/src/Swashbuckle.AspNetCore.Swagger/SwaggerMiddleware.cs b/src/Swashbuckle.AspNetCore.Swagger/SwaggerMiddleware.cs
index 00921b4f8f..8f30d68ac6 100644
--- a/src/Swashbuckle.AspNetCore.Swagger/SwaggerMiddleware.cs
+++ b/src/Swashbuckle.AspNetCore.Swagger/SwaggerMiddleware.cs
@@ -14,7 +14,7 @@
 
 namespace Swashbuckle.AspNetCore.Swagger
 {
-    public class SwaggerMiddleware
+    internal sealed class SwaggerMiddleware
     {
         private readonly RequestDelegate _next;
         private readonly SwaggerOptions _options;
@@ -33,6 +33,7 @@ public SwaggerMiddleware(
         }
 
 #if !NETSTANDARD
+        [ActivatorUtilitiesConstructor]
         public SwaggerMiddleware(
             RequestDelegate next,
             SwaggerOptions options,
diff --git a/src/Swashbuckle.AspNetCore.Swagger/Swashbuckle.AspNetCore.Swagger.csproj b/src/Swashbuckle.AspNetCore.Swagger/Swashbuckle.AspNetCore.Swagger.csproj
index 801dc9e216..377aff8931 100644
--- a/src/Swashbuckle.AspNetCore.Swagger/Swashbuckle.AspNetCore.Swagger.csproj
+++ b/src/Swashbuckle.AspNetCore.Swagger/Swashbuckle.AspNetCore.Swagger.csproj
@@ -8,7 +8,7 @@
     <NoWarn>$(NoWarn);1591</NoWarn>
     <PackageTags>swagger;documentation;discovery;help;webapi;aspnet;aspnetcore</PackageTags>
     <SignAssembly>true</SignAssembly>
-    <TargetFrameworks>netstandard2.0;netcoreapp3.0;net5.0;net6.0;net7.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0;netstandard2.0</TargetFrameworks>
   </PropertyGroup>
   <PropertyGroup Condition="$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net8.0'))">
     <EnableAotAnalyzer>true</EnableAotAnalyzer>
diff --git a/src/Swashbuckle.AspNetCore.SwaggerGen/DependencyInjection/ConfigureSwaggerGeneratorOptions.cs b/src/Swashbuckle.AspNetCore.SwaggerGen/DependencyInjection/ConfigureSwaggerGeneratorOptions.cs
index 28779a0a86..f8e26cda12 100644
--- a/src/Swashbuckle.AspNetCore.SwaggerGen/DependencyInjection/ConfigureSwaggerGeneratorOptions.cs
+++ b/src/Swashbuckle.AspNetCore.SwaggerGen/DependencyInjection/ConfigureSwaggerGeneratorOptions.cs
@@ -6,7 +6,7 @@
 using Microsoft.Extensions.Options;
 using Microsoft.OpenApi.Models;
 
-#if NETSTANDARD2_0
+#if NETSTANDARD
 using IWebHostEnvironment = Microsoft.AspNetCore.Hosting.IHostingEnvironment;
 #endif
 
diff --git a/src/Swashbuckle.AspNetCore.SwaggerGen/SchemaGenerator/SchemaGenerator.cs b/src/Swashbuckle.AspNetCore.SwaggerGen/SchemaGenerator/SchemaGenerator.cs
index 9bb725ee86..7109f4cc2d 100644
--- a/src/Swashbuckle.AspNetCore.SwaggerGen/SchemaGenerator/SchemaGenerator.cs
+++ b/src/Swashbuckle.AspNetCore.SwaggerGen/SchemaGenerator/SchemaGenerator.cs
@@ -228,7 +228,7 @@ private OpenApiSchema GeneratePolymorphicSchema(
             typeof(IFormFile),
             typeof(FileResult),
             typeof(System.IO.Stream),
-#if NETCOREAPP3_0_OR_GREATER
+#if !NETSTANDARD
             typeof(System.IO.Pipelines.PipeReader),
 #endif
         ];
diff --git a/src/Swashbuckle.AspNetCore.SwaggerGen/SwaggerGenerator/ApiParameterDescriptionExtensions.cs b/src/Swashbuckle.AspNetCore.SwaggerGen/SwaggerGenerator/ApiParameterDescriptionExtensions.cs
index e505905e60..a36ed4c778 100644
--- a/src/Swashbuckle.AspNetCore.SwaggerGen/SwaggerGenerator/ApiParameterDescriptionExtensions.cs
+++ b/src/Swashbuckle.AspNetCore.SwaggerGen/SwaggerGenerator/ApiParameterDescriptionExtensions.cs
@@ -49,7 +49,7 @@ public static bool IsRequiredParameter(this ApiParameterDescription apiParameter
 
             // For non-controllers, prefer the IsRequired flag if we're not on netstandard 2.0, otherwise fallback to the default logic.
             return
-#if !NETSTANDARD2_0
+#if !NETSTANDARD
             apiParameter.IsRequired;
 #else
             IsRequired();
@@ -59,7 +59,7 @@ public static bool IsRequiredParameter(this ApiParameterDescription apiParameter
         public static ParameterInfo ParameterInfo(this ApiParameterDescription apiParameter)
         {
             var parameterDescriptor = apiParameter.ParameterDescriptor as
-#if NETCOREAPP2_2_OR_GREATER
+#if !NETSTANDARD
                 Microsoft.AspNetCore.Mvc.Infrastructure.IParameterInfoParameterDescriptor;
 #else
                 ControllerParameterDescriptor;
diff --git a/src/Swashbuckle.AspNetCore.SwaggerGen/Swashbuckle.AspNetCore.SwaggerGen.csproj b/src/Swashbuckle.AspNetCore.SwaggerGen/Swashbuckle.AspNetCore.SwaggerGen.csproj
index 43392c1ebb..aa81b0be06 100644
--- a/src/Swashbuckle.AspNetCore.SwaggerGen/Swashbuckle.AspNetCore.SwaggerGen.csproj
+++ b/src/Swashbuckle.AspNetCore.SwaggerGen/Swashbuckle.AspNetCore.SwaggerGen.csproj
@@ -8,7 +8,7 @@
     <NoWarn>$(NoWarn);1591</NoWarn>
     <PackageTags>swagger;documentation;discovery;help;webapi;aspnet;aspnetcore</PackageTags>
     <SignAssembly>true</SignAssembly>
-    <TargetFrameworks>netstandard2.0;netcoreapp3.0;net5.0;net6.0;net7.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0;netstandard2.0</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/src/Swashbuckle.AspNetCore.SwaggerUI/PublicAPI/.NETCoreApp/PublicAPI.Shipped.txt b/src/Swashbuckle.AspNetCore.SwaggerUI/PublicAPI/.NETCoreApp/PublicAPI.Shipped.txt
deleted file mode 100644
index b4d9e15c71..0000000000
--- a/src/Swashbuckle.AspNetCore.SwaggerUI/PublicAPI/.NETCoreApp/PublicAPI.Shipped.txt
+++ /dev/null
@@ -1 +0,0 @@
-Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIMiddleware.SwaggerUIMiddleware(Microsoft.AspNetCore.Http.RequestDelegate next, Microsoft.AspNetCore.Hosting.IWebHostEnvironment hostingEnv, Microsoft.Extensions.Logging.ILoggerFactory loggerFactory, Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIOptions options) -> void
diff --git a/src/Swashbuckle.AspNetCore.SwaggerUI/PublicAPI/.NETCoreApp/PublicAPI.Unshipped.txt b/src/Swashbuckle.AspNetCore.SwaggerUI/PublicAPI/.NETCoreApp/PublicAPI.Unshipped.txt
deleted file mode 100644
index e69de29bb2..0000000000
diff --git a/src/Swashbuckle.AspNetCore.SwaggerUI/PublicAPI/.NETStandard/PublicAPI.Shipped.txt b/src/Swashbuckle.AspNetCore.SwaggerUI/PublicAPI/.NETStandard/PublicAPI.Shipped.txt
deleted file mode 100644
index e670921146..0000000000
--- a/src/Swashbuckle.AspNetCore.SwaggerUI/PublicAPI/.NETStandard/PublicAPI.Shipped.txt
+++ /dev/null
@@ -1 +0,0 @@
-Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIMiddleware.SwaggerUIMiddleware(Microsoft.AspNetCore.Http.RequestDelegate next, Microsoft.AspNetCore.Hosting.IHostingEnvironment hostingEnv, Microsoft.Extensions.Logging.ILoggerFactory loggerFactory, Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIOptions options) -> void
diff --git a/src/Swashbuckle.AspNetCore.SwaggerUI/PublicAPI/.NETStandard/PublicAPI.Unshipped.txt b/src/Swashbuckle.AspNetCore.SwaggerUI/PublicAPI/.NETStandard/PublicAPI.Unshipped.txt
deleted file mode 100644
index e69de29bb2..0000000000
diff --git a/src/Swashbuckle.AspNetCore.SwaggerUI/PublicAPI/PublicAPI.Shipped.txt b/src/Swashbuckle.AspNetCore.SwaggerUI/PublicAPI/PublicAPI.Shipped.txt
index 457418617a..10a51b8ceb 100644
--- a/src/Swashbuckle.AspNetCore.SwaggerUI/PublicAPI/PublicAPI.Shipped.txt
+++ b/src/Swashbuckle.AspNetCore.SwaggerUI/PublicAPI/PublicAPI.Shipped.txt
@@ -116,8 +116,6 @@ Swashbuckle.AspNetCore.SwaggerUI.SubmitMethod.Patch = 6 -> Swashbuckle.AspNetCor
 Swashbuckle.AspNetCore.SwaggerUI.SubmitMethod.Post = 2 -> Swashbuckle.AspNetCore.SwaggerUI.SubmitMethod
 Swashbuckle.AspNetCore.SwaggerUI.SubmitMethod.Put = 1 -> Swashbuckle.AspNetCore.SwaggerUI.SubmitMethod
 Swashbuckle.AspNetCore.SwaggerUI.SubmitMethod.Trace = 7 -> Swashbuckle.AspNetCore.SwaggerUI.SubmitMethod
-Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIMiddleware
-Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIMiddleware.Invoke(Microsoft.AspNetCore.Http.HttpContext httpContext) -> System.Threading.Tasks.Task
 Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIOptions
 Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIOptions.ConfigObject.get -> Swashbuckle.AspNetCore.SwaggerUI.ConfigObject
 Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIOptions.ConfigObject.set -> void
diff --git a/src/Swashbuckle.AspNetCore.SwaggerUI/SwaggerUIBuilderExtensions.cs b/src/Swashbuckle.AspNetCore.SwaggerUI/SwaggerUIBuilderExtensions.cs
index 0ca25662de..e366fa318f 100644
--- a/src/Swashbuckle.AspNetCore.SwaggerUI/SwaggerUIBuilderExtensions.cs
+++ b/src/Swashbuckle.AspNetCore.SwaggerUI/SwaggerUIBuilderExtensions.cs
@@ -4,7 +4,7 @@
 using Microsoft.Extensions.Options;
 using Swashbuckle.AspNetCore.SwaggerUI;
 
-#if NETSTANDARD2_0
+#if NETSTANDARD
 using IWebHostEnvironment = Microsoft.AspNetCore.Hosting.IHostingEnvironment;
 #endif
 
diff --git a/src/Swashbuckle.AspNetCore.SwaggerUI/SwaggerUIMiddleware.cs b/src/Swashbuckle.AspNetCore.SwaggerUI/SwaggerUIMiddleware.cs
index 96b95be0a0..4a65cb7cf9 100644
--- a/src/Swashbuckle.AspNetCore.SwaggerUI/SwaggerUIMiddleware.cs
+++ b/src/Swashbuckle.AspNetCore.SwaggerUI/SwaggerUIMiddleware.cs
@@ -16,13 +16,13 @@
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
 
-#if NETSTANDARD2_0
+#if NETSTANDARD
 using IWebHostEnvironment = Microsoft.AspNetCore.Hosting.IHostingEnvironment;
 #endif
 
 namespace Swashbuckle.AspNetCore.SwaggerUI
 {
-    public class SwaggerUIMiddleware
+    internal sealed partial class SwaggerUIMiddleware
     {
         private const string EmbeddedFileNamespace = "Swashbuckle.AspNetCore.SwaggerUI.node_modules.swagger_ui_dist";
 
diff --git a/src/Swashbuckle.AspNetCore.SwaggerUI/Swashbuckle.AspNetCore.SwaggerUI.csproj b/src/Swashbuckle.AspNetCore.SwaggerUI/Swashbuckle.AspNetCore.SwaggerUI.csproj
index 1eb5faa1b6..cc5d26da16 100644
--- a/src/Swashbuckle.AspNetCore.SwaggerUI/Swashbuckle.AspNetCore.SwaggerUI.csproj
+++ b/src/Swashbuckle.AspNetCore.SwaggerUI/Swashbuckle.AspNetCore.SwaggerUI.csproj
@@ -8,7 +8,7 @@
     <NoWarn>$(NoWarn);1591</NoWarn>
     <PackageTags>swagger;documentation;discovery;help;webapi;aspnet;aspnetcore</PackageTags>
     <SignAssembly>true</SignAssembly>
-    <TargetFrameworks>netstandard2.0;netcoreapp3.0;net5.0;net6.0;net7.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0;netstandard2.0</TargetFrameworks>
   </PropertyGroup>
   <PropertyGroup Condition="$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net8.0'))">
     <EnableAotAnalyzer>true</EnableAotAnalyzer>
diff --git a/src/Swashbuckle.AspNetCore/Swashbuckle.AspNetCore.csproj b/src/Swashbuckle.AspNetCore/Swashbuckle.AspNetCore.csproj
index 1a85c1f37e..a13077a82e 100644
--- a/src/Swashbuckle.AspNetCore/Swashbuckle.AspNetCore.csproj
+++ b/src/Swashbuckle.AspNetCore/Swashbuckle.AspNetCore.csproj
@@ -13,7 +13,15 @@
     <NuspecFile>$(MSBuildProjectName).nuspec</NuspecFile>
     <PackageId>Swashbuckle.AspNetCore</PackageId>
     <PackageTags>swagger;documentation;discovery;help;webapi;aspnet;aspnetcore</PackageTags>
-    <TargetFrameworks>netstandard2.0;netcoreapp3.0;net5.0;net6.0;net7.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0;netstandard2.0</TargetFrameworks>
+  </PropertyGroup>
+
+  <PropertyGroup Condition=" '$(TargetFramework)' == 'net8.0' ">
+    <MicrosoftExtensionsApiDescriptionServerPackageVersion>8.0.0</MicrosoftExtensionsApiDescriptionServerPackageVersion>
+  </PropertyGroup>
+
+  <PropertyGroup Condition=" '$(TargetFramework)' == 'net9.0' ">
+    <MicrosoftExtensionsApiDescriptionServerPackageVersion>9.0.0</MicrosoftExtensionsApiDescriptionServerPackageVersion>
   </PropertyGroup>
 
   <Target Name="PopulateNuspec">
diff --git a/test/Swashbuckle.AspNetCore.Annotations.Test/Swashbuckle.AspNetCore.Annotations.Test.csproj b/test/Swashbuckle.AspNetCore.Annotations.Test/Swashbuckle.AspNetCore.Annotations.Test.csproj
index 9db709d6b1..55095073dd 100644
--- a/test/Swashbuckle.AspNetCore.Annotations.Test/Swashbuckle.AspNetCore.Annotations.Test.csproj
+++ b/test/Swashbuckle.AspNetCore.Annotations.Test/Swashbuckle.AspNetCore.Annotations.Test.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/test/Swashbuckle.AspNetCore.ApiTesting.Test/Swashbuckle.AspNetCore.ApiTesting.Test.csproj b/test/Swashbuckle.AspNetCore.ApiTesting.Test/Swashbuckle.AspNetCore.ApiTesting.Test.csproj
index 55d738e426..7bbd1da8b5 100644
--- a/test/Swashbuckle.AspNetCore.ApiTesting.Test/Swashbuckle.AspNetCore.ApiTesting.Test.csproj
+++ b/test/Swashbuckle.AspNetCore.ApiTesting.Test/Swashbuckle.AspNetCore.ApiTesting.Test.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/test/Swashbuckle.AspNetCore.Cli.Test/Swashbuckle.AspNetCore.Cli.Test.csproj b/test/Swashbuckle.AspNetCore.Cli.Test/Swashbuckle.AspNetCore.Cli.Test.csproj
index 66198fe569..95477f35e6 100644
--- a/test/Swashbuckle.AspNetCore.Cli.Test/Swashbuckle.AspNetCore.Cli.Test.csproj
+++ b/test/Swashbuckle.AspNetCore.Cli.Test/Swashbuckle.AspNetCore.Cli.Test.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/test/Swashbuckle.AspNetCore.IntegrationTests/Swashbuckle.AspNetCore.IntegrationTests.csproj b/test/Swashbuckle.AspNetCore.IntegrationTests/Swashbuckle.AspNetCore.IntegrationTests.csproj
index 8390f7df37..a872cc305f 100644
--- a/test/Swashbuckle.AspNetCore.IntegrationTests/Swashbuckle.AspNetCore.IntegrationTests.csproj
+++ b/test/Swashbuckle.AspNetCore.IntegrationTests/Swashbuckle.AspNetCore.IntegrationTests.csproj
@@ -4,7 +4,7 @@
     <AssemblyOriginatorKeyFile>$(MSBuildThisFileDirectory)..\..\src\Swashbuckle.AspNetCore.Swagger\Swashbuckle.AspNetCore.Swagger.snk</AssemblyOriginatorKeyFile>
     <NoWarn>$(NoWarn);8002</NoWarn>
     <SignAssembly>true</SignAssembly>
-    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>
@@ -38,8 +38,13 @@
   </ItemGroup>
 
   <ItemGroup Condition="$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net8.0'))">
-    <PackageReference Update="Microsoft.AspNetCore.Mvc.Testing" VersionOverride="8.0.4" />
-    <PackageReference Update="Microsoft.AspNetCore.TestHost" VersionOverride="8.0.4" />
+    <PackageReference Update="Microsoft.AspNetCore.Mvc.Testing" VersionOverride="8.0.11" />
+    <PackageReference Update="Microsoft.AspNetCore.TestHost" VersionOverride="8.0.11" />
+  </ItemGroup>
+
+  <ItemGroup Condition="$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net9.0'))">
+    <PackageReference Update="Microsoft.AspNetCore.Mvc.Testing" VersionOverride="9.0.0" />
+    <PackageReference Update="Microsoft.AspNetCore.TestHost" VersionOverride="9.0.0" />
   </ItemGroup>
 
 </Project>
diff --git a/test/Swashbuckle.AspNetCore.Newtonsoft.Test/Swashbuckle.AspNetCore.Newtonsoft.Test.csproj b/test/Swashbuckle.AspNetCore.Newtonsoft.Test/Swashbuckle.AspNetCore.Newtonsoft.Test.csproj
index 777585bb18..ca6595b9f1 100644
--- a/test/Swashbuckle.AspNetCore.Newtonsoft.Test/Swashbuckle.AspNetCore.Newtonsoft.Test.csproj
+++ b/test/Swashbuckle.AspNetCore.Newtonsoft.Test/Swashbuckle.AspNetCore.Newtonsoft.Test.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/test/Swashbuckle.AspNetCore.SwaggerGen.Test/Swashbuckle.AspNetCore.SwaggerGen.Test.csproj b/test/Swashbuckle.AspNetCore.SwaggerGen.Test/Swashbuckle.AspNetCore.SwaggerGen.Test.csproj
index 950eefb2fa..fb6e0e0b05 100644
--- a/test/Swashbuckle.AspNetCore.SwaggerGen.Test/Swashbuckle.AspNetCore.SwaggerGen.Test.csproj
+++ b/test/Swashbuckle.AspNetCore.SwaggerGen.Test/Swashbuckle.AspNetCore.SwaggerGen.Test.csproj
@@ -3,7 +3,7 @@
   <PropertyGroup>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <NoWarn>1701;1702;1591</NoWarn>
-    <TargetFrameworks>net6.0;net7.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0</TargetFrameworks>
     <SignAssembly>True</SignAssembly>
     <AssemblyOriginatorKeyFile>$(MSBuildThisFileDirectory)..\..\src\Swashbuckle.AspNetCore.Swagger\Swashbuckle.AspNetCore.Swagger.snk</AssemblyOriginatorKeyFile>
   </PropertyGroup>
diff --git a/test/Swashbuckle.AspNetCore.TestSupport/ApiExplorer/ApiDescriptionFactory.cs b/test/Swashbuckle.AspNetCore.TestSupport/ApiExplorer/ApiDescriptionFactory.cs
index 67f4e869ee..338f8695d3 100644
--- a/test/Swashbuckle.AspNetCore.TestSupport/ApiExplorer/ApiDescriptionFactory.cs
+++ b/test/Swashbuckle.AspNetCore.TestSupport/ApiExplorer/ApiDescriptionFactory.cs
@@ -39,11 +39,7 @@ public static ApiDescription Create(
                         .FirstOrDefault(parameterDescriptor => parameterDescriptor.Name == parameter.Name);
 
                     var parameterDescriptorWithParameterInfo = parameter.ParameterDescriptor as
-#if NETCOREAPP2_2_OR_GREATER
                         Microsoft.AspNetCore.Mvc.Infrastructure.IParameterInfoParameterDescriptor;
-#else
-                        ControllerParameterDescriptor;
-#endif
 
                     if (parameterDescriptorWithParameterInfo != null && parameter.ModelMetadata == null)
                     {
diff --git a/test/Swashbuckle.AspNetCore.TestSupport/Swashbuckle.AspNetCore.TestSupport.csproj b/test/Swashbuckle.AspNetCore.TestSupport/Swashbuckle.AspNetCore.TestSupport.csproj
index 4fd2d10b91..dd04fa1bbc 100644
--- a/test/Swashbuckle.AspNetCore.TestSupport/Swashbuckle.AspNetCore.TestSupport.csproj
+++ b/test/Swashbuckle.AspNetCore.TestSupport/Swashbuckle.AspNetCore.TestSupport.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0</TargetFrameworks>
     <IsPackable>false</IsPackable>
     <IsTestProject>false</IsTestProject>
     <VersionPrefix>1.0.0</VersionPrefix>
diff --git a/test/WebSites/Basic/Basic.csproj b/test/WebSites/Basic/Basic.csproj
index dd55d219f3..fa5d21fdd9 100644
--- a/test/WebSites/Basic/Basic.csproj
+++ b/test/WebSites/Basic/Basic.csproj
@@ -3,7 +3,7 @@
   <PropertyGroup>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <NoWarn>$(NoWarn);1591</NoWarn>
-    <TargetFrameworks>netcoreapp3.1;net5.0;net6.0;net7.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/test/WebSites/CliExample/CliExample.csproj b/test/WebSites/CliExample/CliExample.csproj
index 59092cc3b7..86f2f94752 100644
--- a/test/WebSites/CliExample/CliExample.csproj
+++ b/test/WebSites/CliExample/CliExample.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net7.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0</TargetFrameworks>
     <DotNetSwaggerPath>$([System.IO.Path]::Combine('$(ArtifactsPath)', 'bin', 'Swashbuckle.AspNetCore.Cli', '$(Configuration.ToLower())_$(TargetFramework)'))</DotNetSwaggerPath>
   </PropertyGroup>
 
diff --git a/test/WebSites/CliExample/wwwroot/swagger/v1/swagger_net9.0.json b/test/WebSites/CliExample/wwwroot/swagger/v1/swagger_net9.0.json
new file mode 100644
index 0000000000..0e1dee7edd
--- /dev/null
+++ b/test/WebSites/CliExample/wwwroot/swagger/v1/swagger_net9.0.json
@@ -0,0 +1,54 @@
+{
+  "openapi": "3.0.1",
+  "info": {
+    "title": "CliExample",
+    "version": "1.0"
+  },
+  "servers": [
+    {
+      "url": "http://localhost:51071"
+    }
+  ],
+  "paths": {
+    "/products": {
+      "get": {
+        "tags": [
+          "Products"
+        ],
+        "responses": {
+          "200": {
+            "description": "OK",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "type": "array",
+                  "items": {
+                    "$ref": "#/components/schemas/Product"
+                  }
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+  },
+  "components": {
+    "schemas": {
+      "Product": {
+        "type": "object",
+        "properties": {
+          "id": {
+            "type": "integer",
+            "format": "int32"
+          },
+          "description": {
+            "type": "string",
+            "nullable": true
+          }
+        },
+        "additionalProperties": false
+      }
+    }
+  }
+}
\ No newline at end of file
diff --git a/test/WebSites/CliExampleWithFactory/CliExampleWithFactory.csproj b/test/WebSites/CliExampleWithFactory/CliExampleWithFactory.csproj
index 154b9d9f30..9cf5f7a21b 100644
--- a/test/WebSites/CliExampleWithFactory/CliExampleWithFactory.csproj
+++ b/test/WebSites/CliExampleWithFactory/CliExampleWithFactory.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net7.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0</TargetFrameworks>
     <DotNetSwaggerPath>$([System.IO.Path]::Combine('$(ArtifactsPath)', 'bin', 'Swashbuckle.AspNetCore.Cli', '$(Configuration.ToLower())_$(TargetFramework)'))</DotNetSwaggerPath>
   </PropertyGroup>
 
diff --git a/test/WebSites/CliExampleWithFactory/wwwroot/swagger/v1/swagger_net9.0.json b/test/WebSites/CliExampleWithFactory/wwwroot/swagger/v1/swagger_net9.0.json
new file mode 100644
index 0000000000..2778aed45a
--- /dev/null
+++ b/test/WebSites/CliExampleWithFactory/wwwroot/swagger/v1/swagger_net9.0.json
@@ -0,0 +1,54 @@
+{
+  "openapi": "3.0.1",
+  "info": {
+    "title": "CliExampleWithFactory",
+    "version": "1.0"
+  },
+  "servers": [
+    {
+      "url": "http://localhost:57556/"
+    }
+  ],
+  "paths": {
+    "/products": {
+      "get": {
+        "tags": [
+          "Products"
+        ],
+        "responses": {
+          "200": {
+            "description": "OK",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "type": "array",
+                  "items": {
+                    "$ref": "#/components/schemas/Product"
+                  }
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+  },
+  "components": {
+    "schemas": {
+      "Product": {
+        "type": "object",
+        "properties": {
+          "id": {
+            "type": "integer",
+            "format": "int32"
+          },
+          "description": {
+            "type": "string",
+            "nullable": true
+          }
+        },
+        "additionalProperties": false
+      }
+    }
+  }
+}
\ No newline at end of file
diff --git a/test/WebSites/ConfigFromFile/ConfigFromFile.csproj b/test/WebSites/ConfigFromFile/ConfigFromFile.csproj
index c15a19becf..25ceb0900b 100644
--- a/test/WebSites/ConfigFromFile/ConfigFromFile.csproj
+++ b/test/WebSites/ConfigFromFile/ConfigFromFile.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/test/WebSites/CustomDocumentSerializer/CustomDocumentSerializer.csproj b/test/WebSites/CustomDocumentSerializer/CustomDocumentSerializer.csproj
index 997a07e351..8300229ac3 100644
--- a/test/WebSites/CustomDocumentSerializer/CustomDocumentSerializer.csproj
+++ b/test/WebSites/CustomDocumentSerializer/CustomDocumentSerializer.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0</TargetFrameworks>
     <Nullable>enable</Nullable>
     <ImplicitUsings>enable</ImplicitUsings>
     <DotNetSwaggerPath>$([System.IO.Path]::Combine('$(ArtifactsPath)', 'bin', 'Swashbuckle.AspNetCore.Cli', '$(Configuration)_$(TargetFramework)', 'dotnet-swagger.dll'))</DotNetSwaggerPath>
diff --git a/test/WebSites/CustomUIConfig/CustomUIConfig.csproj b/test/WebSites/CustomUIConfig/CustomUIConfig.csproj
index 12c1652b3c..97ee14eb9b 100644
--- a/test/WebSites/CustomUIConfig/CustomUIConfig.csproj
+++ b/test/WebSites/CustomUIConfig/CustomUIConfig.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/test/WebSites/CustomUIIndex/CustomUIIndex.csproj b/test/WebSites/CustomUIIndex/CustomUIIndex.csproj
index 0915fc16fa..edbd3feec5 100644
--- a/test/WebSites/CustomUIIndex/CustomUIIndex.csproj
+++ b/test/WebSites/CustomUIIndex/CustomUIIndex.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/test/WebSites/GenericControllers/GenericControllers.csproj b/test/WebSites/GenericControllers/GenericControllers.csproj
index 5127c90d20..fbf4df6742 100644
--- a/test/WebSites/GenericControllers/GenericControllers.csproj
+++ b/test/WebSites/GenericControllers/GenericControllers.csproj
@@ -3,7 +3,7 @@
   <PropertyGroup>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <NoWarn>$(NoWarn);1591</NoWarn>
-    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/test/WebSites/MinimalApp/MinimalApp.csproj b/test/WebSites/MinimalApp/MinimalApp.csproj
index 997a07e351..8300229ac3 100644
--- a/test/WebSites/MinimalApp/MinimalApp.csproj
+++ b/test/WebSites/MinimalApp/MinimalApp.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0</TargetFrameworks>
     <Nullable>enable</Nullable>
     <ImplicitUsings>enable</ImplicitUsings>
     <DotNetSwaggerPath>$([System.IO.Path]::Combine('$(ArtifactsPath)', 'bin', 'Swashbuckle.AspNetCore.Cli', '$(Configuration)_$(TargetFramework)', 'dotnet-swagger.dll'))</DotNetSwaggerPath>
diff --git a/test/WebSites/MinimalAppWithHostedServices/MinimalAppWithHostedServices.csproj b/test/WebSites/MinimalAppWithHostedServices/MinimalAppWithHostedServices.csproj
index 88afa5f5a3..5b6defe0c6 100644
--- a/test/WebSites/MinimalAppWithHostedServices/MinimalAppWithHostedServices.csproj
+++ b/test/WebSites/MinimalAppWithHostedServices/MinimalAppWithHostedServices.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0</TargetFrameworks>
     <Nullable>enable</Nullable>
     <ImplicitUsings>enable</ImplicitUsings>
     <DotNetSwaggerPath>$([System.IO.Path]::Combine('$(ArtifactsPath)', 'bin', 'Swashbuckle.AspNetCore.Cli', '$(Configuration)_$(TargetFramework)', 'dotnet-swagger.dll'))</DotNetSwaggerPath>
diff --git a/test/WebSites/MultipleVersions/MultipleVersions.csproj b/test/WebSites/MultipleVersions/MultipleVersions.csproj
index 93ff61a200..98d6a6ddcd 100644
--- a/test/WebSites/MultipleVersions/MultipleVersions.csproj
+++ b/test/WebSites/MultipleVersions/MultipleVersions.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/test/WebSites/MvcWithNullable/MvcWithNullable.csproj b/test/WebSites/MvcWithNullable/MvcWithNullable.csproj
index 29f5a084a3..21c72fe119 100644
--- a/test/WebSites/MvcWithNullable/MvcWithNullable.csproj
+++ b/test/WebSites/MvcWithNullable/MvcWithNullable.csproj
@@ -5,7 +5,7 @@
     <NoWarn>$(NoWarn);CA1050</NoWarn>
     <Nullable>enable</Nullable>
     <RootNamespace>WebApi</RootNamespace>
-    <TargetFramework>net8.0</TargetFramework>
+    <TargetFrameworks>net9.0;net8.0</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>
@@ -17,4 +17,8 @@
     <PackageReference Include="Microsoft.AspNetCore.OpenApi" />
   </ItemGroup>
 
+  <ItemGroup Condition="$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net9.0'))">
+    <PackageReference Update="Microsoft.AspNetCore.OpenApi" VersionOverride="9.0.0" />
+  </ItemGroup>
+
 </Project>
diff --git a/test/WebSites/NswagClientExample/NswagClientExample.csproj b/test/WebSites/NswagClientExample/NswagClientExample.csproj
index 6b3282425d..a829b4227c 100644
--- a/test/WebSites/NswagClientExample/NswagClientExample.csproj
+++ b/test/WebSites/NswagClientExample/NswagClientExample.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0</TargetFrameworks>
     <DotNetSwaggerPath>$([System.IO.Path]::Combine('$(ArtifactsPath)', 'bin', 'Swashbuckle.AspNetCore.Cli', '$(Configuration.ToLower())_$(TargetFramework)'))</DotNetSwaggerPath>
     <_NSwagTool>$(NSwagExe_Net60)</_NSwagTool>
     <_NSwagTool Condition="$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net8.0'))">$(NSwagExe_Net80)</_NSwagTool>
diff --git a/test/WebSites/NswagClientExample/swagger_net9.0.json b/test/WebSites/NswagClientExample/swagger_net9.0.json
new file mode 100644
index 0000000000..68e90e3375
--- /dev/null
+++ b/test/WebSites/NswagClientExample/swagger_net9.0.json
@@ -0,0 +1,140 @@
+{
+  "openapi": "3.0.1",
+  "info": {
+    "title": "NswagClientExample",
+    "version": "1.0"
+  },
+  "servers": [
+    {
+      "url": "http://example.com"
+    }
+  ],
+  "paths": {
+    "/Animals": {
+      "post": {
+        "tags": [
+          "Animals"
+        ],
+        "requestBody": {
+          "content": {
+            "application/json": {
+              "schema": {
+                "oneOf": [
+                  {
+                    "$ref": "#/components/schemas/Animal"
+                  },
+                  {
+                    "$ref": "#/components/schemas/Cat"
+                  },
+                  {
+                    "$ref": "#/components/schemas/Dog"
+                  }
+                ]
+              }
+            },
+            "text/json": {
+              "schema": {
+                "oneOf": [
+                  {
+                    "$ref": "#/components/schemas/Animal"
+                  },
+                  {
+                    "$ref": "#/components/schemas/Cat"
+                  },
+                  {
+                    "$ref": "#/components/schemas/Dog"
+                  }
+                ]
+              }
+            },
+            "application/*+json": {
+              "schema": {
+                "oneOf": [
+                  {
+                    "$ref": "#/components/schemas/Animal"
+                  },
+                  {
+                    "$ref": "#/components/schemas/Cat"
+                  },
+                  {
+                    "$ref": "#/components/schemas/Dog"
+                  }
+                ]
+              }
+            }
+          },
+          "required": true
+        },
+        "responses": {
+          "200": {
+            "description": "OK"
+          }
+        }
+      }
+    }
+  },
+  "components": {
+    "schemas": {
+      "Animal": {
+        "required": [
+          "animalType"
+        ],
+        "type": "object",
+        "properties": {
+          "animalType": {
+            "$ref": "#/components/schemas/AnimalType"
+          }
+        },
+        "additionalProperties": false,
+        "discriminator": {
+          "propertyName": "animalType",
+          "mapping": {
+            "Cat": "#/components/schemas/Cat",
+            "Dog": "#/components/schemas/Dog"
+          }
+        }
+      },
+      "AnimalType": {
+        "enum": [
+          "Cat",
+          "Dog"
+        ],
+        "type": "string"
+      },
+      "Cat": {
+        "allOf": [
+          {
+            "$ref": "#/components/schemas/Animal"
+          },
+          {
+            "type": "object",
+            "properties": {
+              "catSpecificProperty": {
+                "type": "string",
+                "nullable": true
+              }
+            },
+            "additionalProperties": false
+          }
+        ]
+      },
+      "Dog": {
+        "allOf": [
+          {
+            "$ref": "#/components/schemas/Animal"
+          },
+          {
+            "type": "object",
+            "properties": {
+              "dogSpecificProperty": {
+                "type": "string",
+                "nullable": true
+              }
+            },
+            "additionalProperties": false
+          }
+        ]
+      }
+    }
+  }
+}
\ No newline at end of file
diff --git a/test/WebSites/OAuth2Integration/OAuth2Integration.csproj b/test/WebSites/OAuth2Integration/OAuth2Integration.csproj
index 6213a123d7..ac9116ab50 100644
--- a/test/WebSites/OAuth2Integration/OAuth2Integration.csproj
+++ b/test/WebSites/OAuth2Integration/OAuth2Integration.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>
@@ -14,4 +14,13 @@
     <ProjectReference Include="..\..\..\src\Swashbuckle.AspNetCore.SwaggerGen\Swashbuckle.AspNetCore.SwaggerGen.csproj" />
     <ProjectReference Include="..\..\..\src\Swashbuckle.AspNetCore.SwaggerUI\Swashbuckle.AspNetCore.SwaggerUI.csproj" />
   </ItemGroup>
+
+  <!--
+    This is just a sample for testing - updating to Duende.IdentityServer can be done at some point in the future.
+    See /~https://github.com/domaindrivendev/Swashbuckle.AspNetCore/issues/3008.
+  -->
+  <ItemGroup>
+    <NuGetAuditSuppress Include="/~https://github.com/advisories/GHSA-55p7-v223-x366" />
+    <NuGetAuditSuppress Include="/~https://github.com/advisories/GHSA-ff4q-64jc-gx98" />
+  </ItemGroup>
 </Project>
diff --git a/test/WebSites/ReDoc/ReDoc.csproj b/test/WebSites/ReDoc/ReDoc.csproj
index a12405310d..3c229ad132 100644
--- a/test/WebSites/ReDoc/ReDoc.csproj
+++ b/test/WebSites/ReDoc/ReDoc.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/test/WebSites/TestFirst.IntegrationTests/TestFirst.IntegrationTests.csproj b/test/WebSites/TestFirst.IntegrationTests/TestFirst.IntegrationTests.csproj
index 62dfbcccd3..a17310c19b 100644
--- a/test/WebSites/TestFirst.IntegrationTests/TestFirst.IntegrationTests.csproj
+++ b/test/WebSites/TestFirst.IntegrationTests/TestFirst.IntegrationTests.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/test/WebSites/TestFirst/TestFirst.csproj b/test/WebSites/TestFirst/TestFirst.csproj
index ef0580e64e..599d9144ea 100644
--- a/test/WebSites/TestFirst/TestFirst.csproj
+++ b/test/WebSites/TestFirst/TestFirst.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/test/WebSites/TopLevelSwaggerDoc/TopLevelSwaggerDoc.csproj b/test/WebSites/TopLevelSwaggerDoc/TopLevelSwaggerDoc.csproj
index 9c90a9ad79..fd35c5d8fb 100644
--- a/test/WebSites/TopLevelSwaggerDoc/TopLevelSwaggerDoc.csproj
+++ b/test/WebSites/TopLevelSwaggerDoc/TopLevelSwaggerDoc.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net6.0</TargetFrameworks>
     <Nullable>enable</Nullable>
     <ImplicitUsings>enable</ImplicitUsings>
   </PropertyGroup>
diff --git a/test/WebSites/WebApi.Aot/WebApi.Aot.csproj b/test/WebSites/WebApi.Aot/WebApi.Aot.csproj
index 70cb09a09d..9d7467fe77 100644
--- a/test/WebSites/WebApi.Aot/WebApi.Aot.csproj
+++ b/test/WebSites/WebApi.Aot/WebApi.Aot.csproj
@@ -5,7 +5,7 @@
     <InvariantGlobalization>true</InvariantGlobalization>
     <Nullable>enable</Nullable>
     <PublishAot>true</PublishAot>
-    <TargetFramework>net8.0</TargetFramework>
+    <TargetFrameworks>net9.0;net8.0</TargetFrameworks>
     <TrimmerSingleWarn>false</TrimmerSingleWarn>
   </PropertyGroup>
 
diff --git a/test/WebSites/WebApi/WebApi.csproj b/test/WebSites/WebApi/WebApi.csproj
index be737b6c89..7b7e13bf21 100644
--- a/test/WebSites/WebApi/WebApi.csproj
+++ b/test/WebSites/WebApi/WebApi.csproj
@@ -4,7 +4,7 @@
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
     <RootNamespace>WebApi</RootNamespace>
-    <TargetFramework>net8.0</TargetFramework>
+    <TargetFrameworks>net9.0;net8.0</TargetFrameworks>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
   </PropertyGroup>
 
@@ -18,4 +18,8 @@
     <PackageReference Include="Microsoft.AspNetCore.OpenApi" />
   </ItemGroup>
 
+  <ItemGroup Condition="$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net9.0'))">
+    <PackageReference Update="Microsoft.AspNetCore.OpenApi" VersionOverride="9.0.0" />
+  </ItemGroup>
+
 </Project>