upgrade C# to protobuf 3.3.0
diff --git a/src/csharp/Grpc.Core/Version.csproj.include b/src/csharp/Grpc.Core/Version.csproj.include
index 6af2af1..8388bfd 100755
--- a/src/csharp/Grpc.Core/Version.csproj.include
+++ b/src/csharp/Grpc.Core/Version.csproj.include
@@ -2,6 +2,6 @@
 <Project>
   <PropertyGroup>
     <GrpcCsharpVersion>1.4.0-dev</GrpcCsharpVersion>
-    <GoogleProtobufVersion>3.2.0</GoogleProtobufVersion>
+    <GoogleProtobufVersion>3.3.0</GoogleProtobufVersion>
   </PropertyGroup>
 </Project>
diff --git a/templates/src/csharp/Grpc.Core/Version.csproj.include.template b/templates/src/csharp/Grpc.Core/Version.csproj.include.template
index 30b8d26..5bc66e9 100755
--- a/templates/src/csharp/Grpc.Core/Version.csproj.include.template
+++ b/templates/src/csharp/Grpc.Core/Version.csproj.include.template
@@ -4,6 +4,6 @@
   <Project>
     <PropertyGroup>
       <GrpcCsharpVersion>${settings.csharp_version}</GrpcCsharpVersion>
-      <GoogleProtobufVersion>3.2.0</GoogleProtobufVersion>
+      <GoogleProtobufVersion>3.3.0</GoogleProtobufVersion>
     </PropertyGroup>
   </Project>