Add support for VB.NET projects

Author: AArnott

Directory.Build.props

@@ -6,7 +6,6 @@
     <BaseIntermediateOutputPath>$(RepoRootPath)obj\$([MSBuild]::MakeRelative($(RepoRootPath), $(MSBuildProjectDirectory)))\</BaseIntermediateOutputPath>
     <BaseOutputPath Condition=" '$(BaseOutputPath)' == '' ">$(RepoRootPath)bin\$(MSBuildProjectName)\</BaseOutputPath>
     <PackageOutputPath>$(RepoRootPath)bin\Packages\$(Configuration)\</PackageOutputPath>
-    <LangVersion>12</LangVersion>
     <Nullable>enable</Nullable>
     <ImplicitUsings>enable</ImplicitUsings>
     <AnalysisLevel>latest</AnalysisLevel>

Directory.Build.targets

@@ -1,5 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project>
+  <PropertyGroup>
+    <LangVersion Condition="'$(Language)'=='C#'">12</LangVersion>
+    <LangVersion Condition="'$(Language)'=='VB'">16.9</LangVersion>
+  </PropertyGroup>
   <ItemGroup>
     <!-- Avoid compile error about missing namespace when combining ImplicitUsings with .NET Framework target frameworks. -->
     <Using Remove="System.Net.Http" Condition="'$(TargetFrameworkIdentifier)'=='.NETFramework'" />

src/AssemblyInfo.vb

@@ -0,0 +1,6 @@
+' Copyright (c) COMPANY-PLACEHOLDER. All rights reserved.
+' Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+Imports System.Runtime.InteropServices
+
+<Assembly: DefaultDllImportSearchPaths(DllImportSearchPath.SafeDirectories)>

src/Directory.Build.targets

@@ -1,7 +1,8 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project>
   <ItemGroup>
-    <Compile Include="$(MSBuildThisFileDirectory)AssemblyInfo.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)AssemblyInfo.cs" Condition=" '$(Language)'=='C#' " />
+    <Compile Include="$(MSBuildThisFileDirectory)AssemblyInfo.vb" Condition=" '$(Language)'=='VB' " />
   </ItemGroup>
 
   <Import Project="$([MSBuild]::GetPathOfFileAbove($(MSBuildThisFile), $(MSBuildThisFileDirectory)..))" />