Merge pull request #19242 from jtattermusch/csharp_easier_net45_build

Get rid of workaround to build net45 targets on linux and mac

src/csharp/Grpc.Core/Common.csproj.include

@@ -19,10 +19,8 @@
     <PublicSign Condition=" '$(OS)' != 'Windows_NT' ">true</PublicSign>
   </PropertyGroup>
 
-  <PropertyGroup Condition="'$(OS)' != 'Windows_NT'">
-    <!-- Workaround for https://github.com/dotnet/sdk/issues/335 -->
-    <FrameworkPathOverride Condition="Exists('/usr/lib/mono/4.5-api')">/usr/lib/mono/4.5-api</FrameworkPathOverride>
-    <FrameworkPathOverride Condition="Exists('/usr/local/lib/mono/4.5-api')">/usr/local/lib/mono/4.5-api</FrameworkPathOverride>
-    <FrameworkPathOverride Condition="Exists('/Library/Frameworks/Mono.framework/Versions/Current/lib/mono/4.5-api')">/Library/Frameworks/Mono.framework/Versions/Current/lib/mono/4.5-api</FrameworkPathOverride>
-  </PropertyGroup>
+  <!-- Needed for the net45 build to work on Unix. See https://github.com/dotnet/designs/pull/33 -->
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.0-preview.2" PrivateAssets="All" />
+  </ItemGroup>
 </Project>

src/csharp/Grpc.Tools.Tests/Grpc.Tools.Tests.csproj

@@ -7,13 +7,10 @@
 
   <Import Project="..\Grpc.Core\SourceLink.csproj.include" />
 
-  <!-- This is copied verbatim from Grpc.Core/Common.csproj.include. Other settings
-       in that file conflict with the intent of this build, as it cannot be signed,
-       and may not compile Grpc.Core/Version.cs, as that file references constants
-       in Grpc.Core.dll.
-       TODO(kkm): Refactor imports. -->
   <PropertyGroup Condition=" '$(OS)' != 'Windows_NT' and '$(MSBuildRuntimeType)' == 'Core' ">
-    <!-- Use Mono reference assemblies in SDK build: https://github.com/dotnet/sdk/issues/335 -->
+    <!-- Use Mono reference assemblies in SDK build: https://github.com/dotnet/sdk/issues/335.
+         This is a different approach than used in Grpc.Core/Common.csproj.include because
+         the workaround used there doesn't seem to be working for Microsoft.Build.* assemblies -->
     <FrameworkPathOverride Condition="Exists('/usr/lib/mono/4.5-api')">/usr/lib/mono/4.5-api</FrameworkPathOverride>
     <FrameworkPathOverride Condition="Exists('/usr/local/lib/mono/4.5-api')">/usr/local/lib/mono/4.5-api</FrameworkPathOverride>
     <FrameworkPathOverride Condition="Exists('/Library/Frameworks/Mono.framework/Versions/Current/lib/mono/4.5-api')">/Library/Frameworks/Mono.framework/Versions/Current/lib/mono/4.5-api</FrameworkPathOverride>

src/csharp/Grpc.Tools/Grpc.Tools.csproj

@@ -7,13 +7,10 @@
     <TargetFrameworks>net45;netstandard1.3</TargetFrameworks>
   </PropertyGroup>
 
-  <!-- This is copied verbatim from Grpc.Core/Common.csproj.include. Other settings
-       in that file conflict with the intent of this build, as it cannot be signed,
-       and may not compile Grpc.Core/Version.cs, as that file references constants
-       in Grpc.Core.dll.
-       TODO(kkm): Refactor imports. -->
   <PropertyGroup Condition=" '$(OS)' != 'Windows_NT' and '$(MSBuildRuntimeType)' == 'Core' ">
-    <!-- Use Mono reference assemblies in SDK build: https://github.com/dotnet/sdk/issues/335 -->
+    <!-- Use Mono reference assemblies in SDK build: https://github.com/dotnet/sdk/issues/335.
+         This is a different approach than used in Grpc.Core/Common.csproj.include because
+         the workaround used there doesn't seem to be working for Microsoft.Build.* assemblies -->
     <FrameworkPathOverride Condition="Exists('/usr/lib/mono/4.5-api')">/usr/lib/mono/4.5-api</FrameworkPathOverride>
     <FrameworkPathOverride Condition="Exists('/usr/local/lib/mono/4.5-api')">/usr/local/lib/mono/4.5-api</FrameworkPathOverride>
     <FrameworkPathOverride Condition="Exists('/Library/Frameworks/Mono.framework/Versions/Current/lib/mono/4.5-api')">/Library/Frameworks/Mono.framework/Versions/Current/lib/mono/4.5-api</FrameworkPathOverride>