--- 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: 07/09/2020 no-loc: ["ASP.NET Core Identity", cookie, Cookie, Blazor, "Blazor Server", "Blazor WebAssembly", "Identity", "Let's Encrypt", Razor, SignalR] 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. [!INCLUDE[](~/includes/gRPCazure.md)] ## proto file gRPC uses a contract-first approach to API development. Protocol buffers (protobuf) are used as the Interface Definition 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 . 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 `HelloReply` message: [!code-protobuf[](~/tutorials/grpc/grpc-start/sample/GrpcGreeter/Protos/greet.proto)] [!INCLUDE[about the series](~/includes/code-comments-loc.md)] ## 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/sample/GrpcGreeter/GrpcGreeter.csproj?highlight=2&range=7-9)] By default, a `` reference generates a concrete client and a service base class. The reference element's `GrpcServices` attribute can be used to limit C# asset generation. Valid `GrpcServices` options are: * `Both` (default when not present) * `Server` * `Client` * `None` ## 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. The `Grpc.AspNetCore` metapackage includes a reference to `Grpc.Tools`. Server projects can add `Grpc.AspNetCore` using the Package Manager in Visual Studio or by adding a `` to the project file: [!code-xml[](~/tutorials/grpc/grpc-start/sample/GrpcGreeter/GrpcGreeter.csproj?highlight=1&range=12)] Client projects should directly reference `Grpc.Tools` alongside the other packages required to use the gRPC client. The tooling package isn't required at runtime, so the dependency is marked with `PrivateAssets="All"`: [!code-xml[](~/tutorials/grpc/grpc-start/sample/GrpcGreeterClient/GrpcGreeterClient.csproj?highlight=3&range=9-11)] ## 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/sample/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.SayHelloAsync` to initiate a gRPC call to the server. [!code-csharp[](~/tutorials/grpc/grpc-start/sample/GrpcGreeterClient/Program.cs?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/sample/GrpcGreeter/GrpcGreeter.csproj?highlight=2&range=7-9)] Similarly, the attribute is set to `Client` in client projects. ## Additional resources * * * *