C# distribtests should test Grpc.Tools codegen too

test/distrib/csharp/DistribTest/DistribTestDotNet.csproj

@@ -16,6 +16,11 @@
     <PackageReference Include="Grpc" Version="__GRPC_NUGET_VERSION__" />
     <PackageReference Include="Grpc.Auth" Version="__GRPC_NUGET_VERSION__" />
     <PackageReference Include="Grpc.Tools" Version="__GRPC_NUGET_VERSION__" />
+    <PackageReference Include="Google.Protobuf" Version="3.7.0" />
+  </ItemGroup>
+  
+  <ItemGroup>
+    <Protobuf Include="**\*.proto" />
   </ItemGroup>
 
   <PropertyGroup Condition="'$(OS)' != 'Windows_NT'">

test/distrib/csharp/DistribTest/testcodegen.proto

@@ -0,0 +1,29 @@
+// Copyright 2019 The gRPC Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+syntax = "proto3";
+
+package testcodegen;
+
+service Greeter {
+  rpc SayHello (HelloRequest) returns (HelloReply) {}
+}
+
+message HelloRequest {
+  string name = 1;
+}
+
+message HelloReply {
+  string message = 1;
+}