upgrade c# Helloworld and RouteGuide to v1.13.1
diff --git a/examples/csharp/Helloworld/Greeter/Greeter.csproj b/examples/csharp/Helloworld/Greeter/Greeter.csproj
index 3bff4a5..3d4be5d 100644
--- a/examples/csharp/Helloworld/Greeter/Greeter.csproj
+++ b/examples/csharp/Helloworld/Greeter/Greeter.csproj
@@ -11,8 +11,8 @@
   <ItemGroup>
     <PackageReference Include="Google.Protobuf" Version="3.5.0" />
     <PackageReference Include="Google.Protobuf.Tools" Version="3.5.0" />
-    <PackageReference Include="Grpc" Version="1.8.0" />
-    <PackageReference Include="Grpc.Tools" Version="1.8.0" />
+    <PackageReference Include="Grpc" Version="1.13.1" />
+    <PackageReference Include="Grpc.Tools" Version="1.13.1" />
   </ItemGroup>
 
 </Project>
diff --git a/examples/csharp/RouteGuide/RouteGuide/RouteGuide.csproj b/examples/csharp/RouteGuide/RouteGuide/RouteGuide.csproj
index 0d9d21f..7419f1a 100644
--- a/examples/csharp/RouteGuide/RouteGuide/RouteGuide.csproj
+++ b/examples/csharp/RouteGuide/RouteGuide/RouteGuide.csproj
@@ -11,8 +11,8 @@
   <ItemGroup>
     <PackageReference Include="Google.Protobuf" Version="3.5.0" />
     <PackageReference Include="Google.Protobuf.Tools" Version="3.5.0" />
-    <PackageReference Include="Grpc" Version="1.8.0" />
-    <PackageReference Include="Grpc.Tools" Version="1.8.0" />
+    <PackageReference Include="Grpc" Version="1.13.1" />
+    <PackageReference Include="Grpc.Tools" Version="1.13.1" />
     <PackageReference Include="Newtonsoft.Json" Version="9.0.1" />
   </ItemGroup>