Update the logic for ProxyAndRecord (#747)

* .

* set

* .

* .

* .

* .

* prio

* appsettings

* TinyMapperUtils

* set

* p

* nullable

* .

* ,

* fs

* .

* .

* --PreferProxyMapping

Directory.Build.props

@@ -13,6 +13,8 @@
         <RepositoryType>git</RepositoryType>
         <RepositoryUrl>https://github.com/WireMock-Net/WireMock.Net</RepositoryUrl>
         <ApplicationIcon>../../resources/WireMock.Net-Logo.ico</ApplicationIcon>
+        <LangVersion>Latest</LangVersion>
+        <Nullable>enable</Nullable>
     </PropertyGroup>
 
     <PropertyGroup Condition="'$(TF_BUILD)' == 'true'">
@@ -24,6 +26,10 @@
         <!--<None Include="../../PackageReadme.md" Pack="true" PackagePath=""/>-->
     </ItemGroup>
 
+    <PropertyGroup Condition="'$(TargetFramework)' != 'net45'">
+        <!--<Nullable>enable</Nullable>-->
+    </PropertyGroup>
+
     <Choose>
         <!-- The environment variable `Prerelease` is set in the azure-pipelines.yml file. -->
         <When Condition=" '$(Prerelease)' != '' ">