Adds NetStandard support for MTLS (#5173)

fix

Co-authored-by: Gladwin Johnson <[email protected]>

Author: gladjohn

build/platform_and_feature_flags.props

@@ -5,7 +5,7 @@
   <PropertyGroup Condition="'$(TargetFramework)' == '$(TargetFrameworkNet)' or '$(TargetFramework)' == '$(TargetFrameworkNetDesktop462)' or '$(TargetFramework)' == '$(TargetFrameworkNetDesktop472)' or '$(TargetFramework)' == '$(TargetFrameworkNetStandard)'">
     <DefineConstants>$(DefineConstants);SUPPORTS_OTEL;</DefineConstants>
   </PropertyGroup>
-  <PropertyGroup Condition="'$(TargetFramework)' == '$(TargetFrameworkNet)' or '$(TargetFramework)' == '$(TargetFrameworkNetDesktop472)'">
+  <PropertyGroup Condition="'$(TargetFramework)' == '$(TargetFrameworkNet)' or '$(TargetFramework)' == '$(TargetFrameworkNetDesktop472)' or '$(TargetFramework)' == '$(TargetFrameworkNetStandard)'">
     <DefineConstants>$(DefineConstants);SUPPORTS_MTLS;</DefineConstants>
   </PropertyGroup>
   <PropertyGroup Condition="'$(TargetFramework)' == '$(TargetFrameworkNetAndroid)'">

src/client/Microsoft.Identity.Client/PlatformsCommon/Shared/SimpleHttpClientFactory.cs

@@ -47,7 +47,7 @@ private static HttpClient CreateMtlsHttpClient(X509Certificate2 bindingCertifica
             }
 
             //Create an HttpClientHandler and configure it to use the client certificate
-            HttpClientHandler handler = new HttpClientHandler();
+            HttpClientHandler handler = new();
 
             handler.ClientCertificates.Add(bindingCertificate);
             var httpClient = new HttpClient(handler);