From 5eef8fe86233897d421f65cb39ba9936f1fbaef9 Mon Sep 17 00:00:00 2001
From: Maxim Lipnin <v-maxlip@microsoft.com>
Date: Wed, 14 Oct 2020 19:07:36 +0300
Subject: [PATCH 1/2] Modify System.Net.HttpListener to throw PNSE at assembly
 level on browser

---
 .../System.Net.HttpListener/Directory.Build.props        | 1 +
 .../ref/System.Net.HttpListener.cs                       | 9 +--------
 .../System.Net.HttpListener/src/Resources/Strings.resx   | 3 +++
 .../src/System.Net.HttpListener.csproj                   | 7 ++++---
 .../src/System/Net/HttpListener.cs                       | 2 --
 .../src/System/Net/HttpListenerRequest.cs                | 5 ++---
 .../System/Net/Managed/HttpListenerRequest.Managed.cs    | 3 ---
 .../System/Net/Managed/HttpListenerResponse.Managed.cs   | 4 ----
 .../Net/Managed/HttpListenerTimeoutManager.Managed.cs    | 2 --
 .../System/Net/Windows/HttpListenerRequest.Windows.cs    | 3 ---
 .../System/Net/Windows/HttpListenerResponse.Windows.cs   | 4 ----
 .../Net/Windows/HttpListenerTimeoutManager.Windows.cs    | 1 -
 .../System.Net.HttpListener/tests/AssemblyInfo.cs        | 6 ++++++
 .../tests/System.Net.HttpListener.Tests.csproj           | 2 ++
 14 files changed, 19 insertions(+), 33 deletions(-)
 create mode 100644 src/libraries/System.Net.HttpListener/tests/AssemblyInfo.cs

diff --git a/src/libraries/System.Net.HttpListener/Directory.Build.props b/src/libraries/System.Net.HttpListener/Directory.Build.props
index 1db5968484c1ec..4784967b7f86ac 100644
--- a/src/libraries/System.Net.HttpListener/Directory.Build.props
+++ b/src/libraries/System.Net.HttpListener/Directory.Build.props
@@ -3,5 +3,6 @@
   <PropertyGroup>
     <StrongNameKeyId>Open</StrongNameKeyId>
     <IncludePlatformAttributes>true</IncludePlatformAttributes>
+    <UnsupportedOSPlatforms>browser</UnsupportedOSPlatforms>
   </PropertyGroup>
 </Project>
\ No newline at end of file
diff --git a/src/libraries/System.Net.HttpListener/ref/System.Net.HttpListener.cs b/src/libraries/System.Net.HttpListener/ref/System.Net.HttpListener.cs
index cdca2d97d4fe9d..b9bf091ebab1ee 100644
--- a/src/libraries/System.Net.HttpListener/ref/System.Net.HttpListener.cs
+++ b/src/libraries/System.Net.HttpListener/ref/System.Net.HttpListener.cs
@@ -13,7 +13,7 @@ public HttpListener() { }
         public System.Net.AuthenticationSchemes AuthenticationSchemes { get { throw null; } set { } }
         public System.Net.AuthenticationSchemeSelector? AuthenticationSchemeSelectorDelegate { get { throw null; } set { } }
         public System.Security.Authentication.ExtendedProtection.ServiceNameCollection DefaultServiceNames { get { throw null; } }
-        public System.Security.Authentication.ExtendedProtection.ExtendedProtectionPolicy ExtendedProtectionPolicy { get { throw null; } [System.Runtime.Versioning.UnsupportedOSPlatformAttribute("browser")] set { } }
+        public System.Security.Authentication.ExtendedProtection.ExtendedProtectionPolicy ExtendedProtectionPolicy { get { throw null; } set { } }
         [System.Diagnostics.CodeAnalysis.DisallowNullAttribute]
         public System.Net.HttpListener.ExtendedProtectionSelector? ExtendedProtectionSelectorDelegate { get { throw null; } set { } }
         public bool IgnoreWriteExceptions { get { throw null; } set { } }
@@ -87,17 +87,14 @@ internal HttpListenerRequest() { }
         public string HttpMethod { get { throw null; } }
         public System.IO.Stream InputStream { get { throw null; } }
         public bool IsAuthenticated { get { throw null; } }
-        [System.Runtime.Versioning.UnsupportedOSPlatformAttribute("browser")]
         public bool IsLocal { get { throw null; } }
         public bool IsSecureConnection { get { throw null; } }
         public bool IsWebSocketRequest { get { throw null; } }
         public bool KeepAlive { get { throw null; } }
-        [System.Runtime.Versioning.UnsupportedOSPlatformAttribute("browser")]
         public System.Net.IPEndPoint LocalEndPoint { get { throw null; } }
         public System.Version ProtocolVersion { get { throw null; } }
         public System.Collections.Specialized.NameValueCollection QueryString { get { throw null; } }
         public string? RawUrl { get { throw null; } }
-        [System.Runtime.Versioning.UnsupportedOSPlatformAttribute("browser")]
         public System.Net.IPEndPoint RemoteEndPoint { get { throw null; } }
         public System.Guid RequestTraceIdentifier { get { throw null; } }
         public string? ServiceName { get { throw null; } }
@@ -105,7 +102,6 @@ internal HttpListenerRequest() { }
         public System.Uri? Url { get { throw null; } }
         public System.Uri? UrlReferrer { get { throw null; } }
         public string UserAgent { get { throw null; } }
-        [System.Runtime.Versioning.UnsupportedOSPlatformAttribute("browser")]
         public string UserHostAddress { get { throw null; } }
         public string UserHostName { get { throw null; } }
         public string[]? UserLanguages { get { throw null; } }
@@ -129,14 +125,11 @@ internal HttpListenerResponse() { }
         public bool SendChunked { get { throw null; } set { } }
         public int StatusCode { get { throw null; } set { } }
         public string StatusDescription { get { throw null; } set { } }
-        [System.Runtime.Versioning.UnsupportedOSPlatformAttribute("browser")]
         public void Abort() { }
         public void AddHeader(string name, string value) { }
         public void AppendCookie(System.Net.Cookie cookie) { }
         public void AppendHeader(string name, string value) { }
-        [System.Runtime.Versioning.UnsupportedOSPlatformAttribute("browser")]
         public void Close() { }
-        [System.Runtime.Versioning.UnsupportedOSPlatformAttribute("browser")]
         public void Close(byte[] responseEntity, bool willBlock) { }
         public void CopyFrom(System.Net.HttpListenerResponse templateResponse) { }
         public void Redirect(string url) { }
diff --git a/src/libraries/System.Net.HttpListener/src/Resources/Strings.resx b/src/libraries/System.Net.HttpListener/src/Resources/Strings.resx
index f9747a646f6a33..c9c146f360c39e 100644
--- a/src/libraries/System.Net.HttpListener/src/Resources/Strings.resx
+++ b/src/libraries/System.Net.HttpListener/src/Resources/Strings.resx
@@ -389,4 +389,7 @@
   <data name="net_WebSockets_InvalidState" xml:space="preserve">
     <value>The WebSocket is in an invalid state ('{0}') for this operation. Valid states are: '{1}'</value>
   </data>
+  <data name="SystemNetHttpListener_PlatformNotSupported" xml:space="preserve">
+    <value>System.Net.HttpListener is not supported on this platform.</value>
+  </data>
 </root>
\ No newline at end of file
diff --git a/src/libraries/System.Net.HttpListener/src/System.Net.HttpListener.csproj b/src/libraries/System.Net.HttpListener/src/System.Net.HttpListener.csproj
index 476f5987eb069a..26703597e17070 100644
--- a/src/libraries/System.Net.HttpListener/src/System.Net.HttpListener.csproj
+++ b/src/libraries/System.Net.HttpListener/src/System.Net.HttpListener.csproj
@@ -4,8 +4,9 @@
     <ForceManagedImplementation>false</ForceManagedImplementation>
     <TargetFrameworks>$(NetCoreAppCurrent)-Windows_NT;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
     <Nullable>enable</Nullable>
+    <GeneratePlatformNotSupportedAssemblyMessage Condition="'$(TargetsBrowser)' == 'true'">SR.SystemNetHttpListener_PlatformNotSupported</GeneratePlatformNotSupportedAssemblyMessage>
   </PropertyGroup>
-  <ItemGroup>
+  <ItemGroup Condition="'$(TargetsBrowser)' != 'true'">
     <ProjectReference Include="$(LibrariesProjectRoot)System.Security.Principal.Windows\src\System.Security.Principal.Windows.csproj" />
     <Reference Include="Microsoft.Win32.Primitives" />
     <Reference Include="System.Collections" />
@@ -33,7 +34,7 @@
     <Reference Include="System.Threading" />
     <Reference Include="System.Threading.Overlapped" />
   </ItemGroup>
-  <ItemGroup>
+  <ItemGroup Condition="'$(TargetsBrowser)' != 'true'">
     <Compile Include="System\Net\BoundaryType.cs" />
     <Compile Include="System\Net\EntitySendFormat.cs" />
     <Compile Include="System\Net\HttpListenerPrefixCollection.cs" />
@@ -247,7 +248,7 @@
     <Compile Include="$(CommonPath)Interop\Windows\SspiCli\SSPIWrapper.cs"
              Link="Common\Interop\Windows\SspiCli\SSPIWrapper.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetsUnix)' == 'true' or '$(TargetsBrowser)' == 'true' or '$(ForceManagedImplementation)' == 'true'">
+  <ItemGroup Condition="'$(TargetsUnix)' == 'true' or '$(ForceManagedImplementation)' == 'true' and '$(TargetsBrowser)' != 'true'">
     <Compile Include="System\Net\Managed\HttpEndPointListener.cs" />
     <Compile Include="System\Net\Managed\HttpEndPointManager.cs" />
     <Compile Include="System\Net\Managed\HttpConnection.cs" />
diff --git a/src/libraries/System.Net.HttpListener/src/System/Net/HttpListener.cs b/src/libraries/System.Net.HttpListener/src/System/Net/HttpListener.cs
index d40826ba07710e..b391474791591f 100644
--- a/src/libraries/System.Net.HttpListener/src/System/Net/HttpListener.cs
+++ b/src/libraries/System.Net.HttpListener/src/System/Net/HttpListener.cs
@@ -3,7 +3,6 @@
 
 using System.Collections;
 using System.Diagnostics.CodeAnalysis;
-using System.Runtime.Versioning;
 using System.Security.Authentication.ExtendedProtection;
 using System.Text;
 using System.Threading.Tasks;
@@ -82,7 +81,6 @@ public AuthenticationSchemes AuthenticationSchemes
         public ExtendedProtectionPolicy ExtendedProtectionPolicy
         {
             get => _extendedProtectionPolicy;
-            [UnsupportedOSPlatform("browser")]
             set
             {
                 CheckDisposed();
diff --git a/src/libraries/System.Net.HttpListener/src/System/Net/HttpListenerRequest.cs b/src/libraries/System.Net.HttpListener/src/System/Net/HttpListenerRequest.cs
index a431ed61e3fc63..1bcab0238d2a1e 100644
--- a/src/libraries/System.Net.HttpListener/src/System/Net/HttpListenerRequest.cs
+++ b/src/libraries/System.Net.HttpListener/src/System/Net/HttpListenerRequest.cs
@@ -7,7 +7,6 @@
 using System.Globalization;
 using System.Net.WebSockets;
 using System.Reflection;
-using System.Runtime.Versioning;
 using System.Security.Cryptography.X509Certificates;
 using System.Text;
 using System.Threading.Tasks;
@@ -111,7 +110,7 @@ public Encoding ContentEncoding
 
         public string? ContentType => Headers[HttpKnownHeaderNames.ContentType];
 
-        [UnsupportedOSPlatform("browser")]
+        
         public bool IsLocal => LocalEndPoint!.Address.Equals(RemoteEndPoint!.Address);
 
         public bool IsWebSocketRequest
@@ -208,7 +207,7 @@ public NameValueCollection QueryString
 
         public string UserAgent => Headers[HttpKnownHeaderNames.UserAgent]!;
 
-        [UnsupportedOSPlatform("browser")]
+        
         public string UserHostAddress => LocalEndPoint!.ToString();
 
         public string UserHostName => Headers[HttpKnownHeaderNames.Host]!;
diff --git a/src/libraries/System.Net.HttpListener/src/System/Net/Managed/HttpListenerRequest.Managed.cs b/src/libraries/System.Net.HttpListener/src/System/Net/Managed/HttpListenerRequest.Managed.cs
index a29021d572f659..cdcda5884bd819 100644
--- a/src/libraries/System.Net.HttpListener/src/System/Net/Managed/HttpListenerRequest.Managed.cs
+++ b/src/libraries/System.Net.HttpListener/src/System/Net/Managed/HttpListenerRequest.Managed.cs
@@ -35,7 +35,6 @@
 using System.Diagnostics;
 using System.Globalization;
 using System.IO;
-using System.Runtime.Versioning;
 using System.Security.Authentication.ExtendedProtection;
 using System.Security.Cryptography.X509Certificates;
 using System.Text;
@@ -375,10 +374,8 @@ public Stream InputStream
 
         public bool IsSecureConnection => _context.Connection.IsSecure;
 
-        [UnsupportedOSPlatform("browser")]
         public IPEndPoint? LocalEndPoint => _context.Connection.LocalEndPoint;
 
-        [UnsupportedOSPlatform("browser")]
         public IPEndPoint? RemoteEndPoint => _context.Connection.RemoteEndPoint;
 
         public Guid RequestTraceIdentifier { get; } = Guid.NewGuid();
diff --git a/src/libraries/System.Net.HttpListener/src/System/Net/Managed/HttpListenerResponse.Managed.cs b/src/libraries/System.Net.HttpListener/src/System/Net/Managed/HttpListenerResponse.Managed.cs
index 4de98bf987c458..2a8fc6efd38729 100644
--- a/src/libraries/System.Net.HttpListener/src/System/Net/Managed/HttpListenerResponse.Managed.cs
+++ b/src/libraries/System.Net.HttpListener/src/System/Net/Managed/HttpListenerResponse.Managed.cs
@@ -31,7 +31,6 @@
 
 using System.Globalization;
 using System.IO;
-using System.Runtime.Versioning;
 using System.Text;
 
 namespace System.Net
@@ -94,7 +93,6 @@ public int StatusCode
 
         private void Dispose() => Close(true);
 
-        [UnsupportedOSPlatform("browser")]
         public void Close()
         {
             if (Disposed)
@@ -103,7 +101,6 @@ public void Close()
             Close(false);
         }
 
-        [UnsupportedOSPlatform("browser")]
         public void Abort()
         {
             if (Disposed)
@@ -118,7 +115,6 @@ private void Close(bool force)
             _httpContext!.Connection.Close(force);
         }
 
-        [UnsupportedOSPlatform("browser")]
         public void Close(byte[] responseEntity, bool willBlock)
         {
             CheckDisposed();
diff --git a/src/libraries/System.Net.HttpListener/src/System/Net/Managed/HttpListenerTimeoutManager.Managed.cs b/src/libraries/System.Net.HttpListener/src/System/Net/Managed/HttpListenerTimeoutManager.Managed.cs
index 8dda7441040797..6194cf1b952111 100644
--- a/src/libraries/System.Net.HttpListener/src/System/Net/Managed/HttpListenerTimeoutManager.Managed.cs
+++ b/src/libraries/System.Net.HttpListener/src/System/Net/Managed/HttpListenerTimeoutManager.Managed.cs
@@ -1,8 +1,6 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-using System.Runtime.Versioning;
-
 namespace System.Net
 {
     public class HttpListenerTimeoutManager
diff --git a/src/libraries/System.Net.HttpListener/src/System/Net/Windows/HttpListenerRequest.Windows.cs b/src/libraries/System.Net.HttpListener/src/System/Net/Windows/HttpListenerRequest.Windows.cs
index b49eb2c1f1a21c..c3b038a3f083fe 100644
--- a/src/libraries/System.Net.HttpListener/src/System/Net/Windows/HttpListenerRequest.Windows.cs
+++ b/src/libraries/System.Net.HttpListener/src/System/Net/Windows/HttpListenerRequest.Windows.cs
@@ -7,7 +7,6 @@
 using System.IO;
 using System.Net.WebSockets;
 using System.Runtime.InteropServices;
-using System.Runtime.Versioning;
 using System.Security;
 using System.Security.Authentication.ExtendedProtection;
 using System.Security.Cryptography;
@@ -289,7 +288,6 @@ public bool HasEntityBody
             }
         }
 
-        [UnsupportedOSPlatform("browser")]
         public IPEndPoint RemoteEndPoint
         {
             get
@@ -303,7 +301,6 @@ public IPEndPoint RemoteEndPoint
             }
         }
 
-        [UnsupportedOSPlatform("browser")]
         public IPEndPoint LocalEndPoint
         {
             get
diff --git a/src/libraries/System.Net.HttpListener/src/System/Net/Windows/HttpListenerResponse.Windows.cs b/src/libraries/System.Net.HttpListener/src/System/Net/Windows/HttpListenerResponse.Windows.cs
index 40d72e8af468b8..0c4b36af8efc75 100644
--- a/src/libraries/System.Net.HttpListener/src/System/Net/Windows/HttpListenerResponse.Windows.cs
+++ b/src/libraries/System.Net.HttpListener/src/System/Net/Windows/HttpListenerResponse.Windows.cs
@@ -8,7 +8,6 @@
 using System.Text;
 using System.ComponentModel;
 using System.Diagnostics;
-using System.Runtime.Versioning;
 using Microsoft.Win32.SafeHandles;
 
 namespace System.Net
@@ -96,7 +95,6 @@ public Version ProtocolVersion
             }
         }
 
-        [UnsupportedOSPlatform("browser")]
         public void Abort()
         {
             if (Disposed)
@@ -108,7 +106,6 @@ public void Abort()
             HttpListenerContext.Abort();
         }
 
-        [UnsupportedOSPlatform("browser")]
         public void Close()
         {
             try
@@ -121,7 +118,6 @@ public void Close()
             }
         }
 
-        [UnsupportedOSPlatform("browser")]
         public void Close(byte[] responseEntity, bool willBlock)
         {
             CheckDisposed();
diff --git a/src/libraries/System.Net.HttpListener/src/System/Net/Windows/HttpListenerTimeoutManager.Windows.cs b/src/libraries/System.Net.HttpListener/src/System/Net/Windows/HttpListenerTimeoutManager.Windows.cs
index a1af5b35b71a84..1e51688fea6e79 100644
--- a/src/libraries/System.Net.HttpListener/src/System/Net/Windows/HttpListenerTimeoutManager.Windows.cs
+++ b/src/libraries/System.Net.HttpListener/src/System/Net/Windows/HttpListenerTimeoutManager.Windows.cs
@@ -2,7 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Diagnostics;
-using System.Runtime.Versioning;
 
 namespace System.Net
 {
diff --git a/src/libraries/System.Net.HttpListener/tests/AssemblyInfo.cs b/src/libraries/System.Net.HttpListener/tests/AssemblyInfo.cs
new file mode 100644
index 00000000000000..be691cadde455f
--- /dev/null
+++ b/src/libraries/System.Net.HttpListener/tests/AssemblyInfo.cs
@@ -0,0 +1,6 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Xunit;
+
+[assembly: SkipOnMono("System.Net.HttpListener is not supported on wasm", TestPlatforms.Browser)]
\ No newline at end of file
diff --git a/src/libraries/System.Net.HttpListener/tests/System.Net.HttpListener.Tests.csproj b/src/libraries/System.Net.HttpListener/tests/System.Net.HttpListener.Tests.csproj
index 3d8ebf1e50be37..2cb8e45108846b 100644
--- a/src/libraries/System.Net.HttpListener/tests/System.Net.HttpListener.Tests.csproj
+++ b/src/libraries/System.Net.HttpListener/tests/System.Net.HttpListener.Tests.csproj
@@ -3,8 +3,10 @@
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <StringResourcesPath>../src/Resources/Strings.resx</StringResourcesPath>
     <TargetFrameworks>$(NetCoreAppCurrent)-Windows_NT;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser;$(NetCoreAppCurrent)-OSX</TargetFrameworks>
+    <IgnoreForCI Condition="'$(TargetOS)' == 'Browser'">true</IgnoreForCI>
   </PropertyGroup>
   <ItemGroup>
+    <Compile Include="AssemblyInfo.cs" />
     <Compile Include="GetContextHelper.cs" />
     <Compile Include="HttpListenerFactory.cs" />
     <Compile Include="HttpListenerAuthenticationTests.cs" />

From fdb3faa83509b4021a9705bcafe949c713c63b77 Mon Sep 17 00:00:00 2001
From: Maxim Lipnin <v-maxlip@microsoft.com>
Date: Thu, 15 Oct 2020 11:46:08 +0300
Subject: [PATCH 2/2] Fix build

---
 .../src/System.Net.HttpListener.csproj                        | 4 ++--
 .../src/System/Net/HttpListenerRequest.cs                     | 2 --
 .../System/Net/Managed/HttpListenerTimeoutManager.Managed.cs  | 2 ++
 .../System/Net/Windows/HttpListenerTimeoutManager.Windows.cs  | 1 +
 4 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/libraries/System.Net.HttpListener/src/System.Net.HttpListener.csproj b/src/libraries/System.Net.HttpListener/src/System.Net.HttpListener.csproj
index 26703597e17070..c0af10c41b83b5 100644
--- a/src/libraries/System.Net.HttpListener/src/System.Net.HttpListener.csproj
+++ b/src/libraries/System.Net.HttpListener/src/System.Net.HttpListener.csproj
@@ -6,7 +6,7 @@
     <Nullable>enable</Nullable>
     <GeneratePlatformNotSupportedAssemblyMessage Condition="'$(TargetsBrowser)' == 'true'">SR.SystemNetHttpListener_PlatformNotSupported</GeneratePlatformNotSupportedAssemblyMessage>
   </PropertyGroup>
-  <ItemGroup Condition="'$(TargetsBrowser)' != 'true'">
+  <ItemGroup>
     <ProjectReference Include="$(LibrariesProjectRoot)System.Security.Principal.Windows\src\System.Security.Principal.Windows.csproj" />
     <Reference Include="Microsoft.Win32.Primitives" />
     <Reference Include="System.Collections" />
@@ -248,7 +248,7 @@
     <Compile Include="$(CommonPath)Interop\Windows\SspiCli\SSPIWrapper.cs"
              Link="Common\Interop\Windows\SspiCli\SSPIWrapper.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetsUnix)' == 'true' or '$(ForceManagedImplementation)' == 'true' and '$(TargetsBrowser)' != 'true'">
+  <ItemGroup Condition="'$(TargetsUnix)' == 'true' or '$(ForceManagedImplementation)' == 'true'">
     <Compile Include="System\Net\Managed\HttpEndPointListener.cs" />
     <Compile Include="System\Net\Managed\HttpEndPointManager.cs" />
     <Compile Include="System\Net\Managed\HttpConnection.cs" />
diff --git a/src/libraries/System.Net.HttpListener/src/System/Net/HttpListenerRequest.cs b/src/libraries/System.Net.HttpListener/src/System/Net/HttpListenerRequest.cs
index 1bcab0238d2a1e..4540239e76b4e9 100644
--- a/src/libraries/System.Net.HttpListener/src/System/Net/HttpListenerRequest.cs
+++ b/src/libraries/System.Net.HttpListener/src/System/Net/HttpListenerRequest.cs
@@ -110,7 +110,6 @@ public Encoding ContentEncoding
 
         public string? ContentType => Headers[HttpKnownHeaderNames.ContentType];
 
-        
         public bool IsLocal => LocalEndPoint!.Address.Equals(RemoteEndPoint!.Address);
 
         public bool IsWebSocketRequest
@@ -207,7 +206,6 @@ public NameValueCollection QueryString
 
         public string UserAgent => Headers[HttpKnownHeaderNames.UserAgent]!;
 
-        
         public string UserHostAddress => LocalEndPoint!.ToString();
 
         public string UserHostName => Headers[HttpKnownHeaderNames.Host]!;
diff --git a/src/libraries/System.Net.HttpListener/src/System/Net/Managed/HttpListenerTimeoutManager.Managed.cs b/src/libraries/System.Net.HttpListener/src/System/Net/Managed/HttpListenerTimeoutManager.Managed.cs
index 6194cf1b952111..8dda7441040797 100644
--- a/src/libraries/System.Net.HttpListener/src/System/Net/Managed/HttpListenerTimeoutManager.Managed.cs
+++ b/src/libraries/System.Net.HttpListener/src/System/Net/Managed/HttpListenerTimeoutManager.Managed.cs
@@ -1,6 +1,8 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Runtime.Versioning;
+
 namespace System.Net
 {
     public class HttpListenerTimeoutManager
diff --git a/src/libraries/System.Net.HttpListener/src/System/Net/Windows/HttpListenerTimeoutManager.Windows.cs b/src/libraries/System.Net.HttpListener/src/System/Net/Windows/HttpListenerTimeoutManager.Windows.cs
index 1e51688fea6e79..a1af5b35b71a84 100644
--- a/src/libraries/System.Net.HttpListener/src/System/Net/Windows/HttpListenerTimeoutManager.Windows.cs
+++ b/src/libraries/System.Net.HttpListener/src/System/Net/Windows/HttpListenerTimeoutManager.Windows.cs
@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Diagnostics;
+using System.Runtime.Versioning;
 
 namespace System.Net
 {