AspNetCore.Docs/aspnetcore/grpc/basics.md

title	author	description	monikerRange	ms.author	ms.date	no-loc	uid
gRPC services with C#	juntaoluo	Learn the basic concepts when writing gRPC services with C#.	>= aspnetcore-3.0	johluo	07/09/2020	ASP.NET Core Identity cookie Cookie Blazor Blazor Server Blazor WebAssembly Identity Let's Encrypt Razor SignalR	grpc/basics

gRPC services with C#

This document outlines the concepts needed to write gRPC apps in C#. The topics covered here apply to both C-core-based and ASP.NET Core-based gRPC apps.

[!INCLUDE]

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 xref:grpc/protobuf.

For example, consider the greet.proto file used in Get started with gRPC service:

• Defines a Greeter service.
• The Greeter service defines a SayHello call.
• SayHello sends a HelloRequest message and receives a HelloReply message:

[!code-protobuf] [!INCLUDEabout the series]

Add a .proto file to a C# app

The *.proto file is included in a project by adding it to the <Protobuf> item group:

[!code-xml]

By default, a <Protobuf> 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 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 <PackageReference> to the project file:

[!code-xml]

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]

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]

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]

By default, server and client assets are generated for each *.proto file included in the <Protobuf> item group. To ensure only the server assets are generated in a server project, the GrpcServices attribute is set to Server.

[!code-xml]

Similarly, the attribute is set to Client in client projects.

Additional resources

• xref:grpc/index
• xref:tutorials/grpc/grpc-start
• xref:grpc/aspnetcore
• xref:grpc/client