--- title: gRPC services with C# author: juntaoluo description: Learn the basic concepts when writing gRPC services with C#. monikerRange: '>= aspnetcore-3.0' ms.author: johluo ms.date: 03/31/2019 uid: grpc/basics --- # gRPC services with C\# This document outlines the concepts needed to write [gRPC](https://grpc.io/docs/guides/) apps in C#. The topics covered here apply to both [C-core](https://grpc.io/blog/grpc-stacks)-based and ASP.NET Core-based gRPC apps. ## proto file gRPC uses a contract-first approach to API development. Protocol buffers (protobuf) are used as the Interface Design Language (IDL) by default. The *.proto* file contains: * The definition of the gRPC service. * The messages sent between clients and servers. For more information on the syntax of protobuf files, see the [official documentation (protobuf)](https://developers.google.com/protocol-buffers/docs/proto3). For example, consider the *greet.proto* file used in [Get started with gRPC service](xref:tutorials/grpc/grpc-start): * Defines a `Greeter` service. * The `Greeter` service defines a `SayHello` call. * `SayHello` sends a `HelloRequest` message and receives a `HelloResponse` message: [!code-proto[](~/tutorials/grpc/grpc-start/samples/GrpcGreeter/Protos/greet.proto)] ## Add a .proto file to a C\# app The *.proto* file is included in a project by adding it to the `` item group: [!code-xml[](~/tutorials/grpc/grpc-start/samples/GrpcGreeter/GrpcGreeter.csproj?highlight=2&range=7-11)] ## C# Tooling support for .proto files The tooling package [Grpc.Tools](https://www.nuget.org/packages/Grpc.Tools/) is required to generate the C# assets from *.proto* files. The generated assets (files): * Are generated on an as-needed basis each time the project is built. * Aren't added to the project or checked into source control. * Are a build artifact contained in the *obj* directory. This package is required by both the server and client projects. `Grpc.Tools` can be added by using the Package Manager in Visual Studio or adding a `` to the project file: [!code-xml[](~/tutorials/grpc/grpc-start/samples/GrpcGreeter/GrpcGreeter.csproj?highlight=1&range=17)] The tooling package isn't required at runtime, so the dependency is marked with `PrivateAssets="All"`. ## Generated C# assets The tooling package generates the C# types representing the messages defined in the included *.proto* files. For server-side assets, an abstract service base type is generated. The base type contains the definitions of all the gRPC calls contained in the *.proto* file. Create a concrete service implementation that derives from this base type and implements the logic for the gRPC calls. For the `greet.proto`, the example described previously, an abstract `GreeterBase` type that contains a virtual `SayHello` method is generated. A concrete implementation `GreeterService` overrides the method and implements the logic handling the gRPC call. [!code-csharp[](~/tutorials/grpc/grpc-start/samples/GrpcGreeter/Services/GreeterService.cs?name=snippet)] For client-side assets, a concrete client type is generated. The gRPC calls in the *.proto* file are translated into methods on the concrete type, which can be called. For the `greet.proto`, the example described previously, a concrete `GreeterClient` type is generated. Call `GreeterClient.SayHello` to initiate a gRPC call to the server. [!code-csharp[](~/tutorials/grpc/grpc-start/samples/GrpcGreeterClient/Program.cs?highlight=5-8&name=snippet)] By default, server and client assets are generated for each *.proto* file included in the `` item group. To ensure only the server assets are generated in a server project, the `GrpcServices` attribute is set to `Server`. [!code-xml[](~/tutorials/grpc/grpc-start/samples/GrpcGreeter/GrpcGreeter.csproj?highlight=2&range=7-11)] Similarly, the attribute is set to `Client` in client projects. ## Additional resources * * * *