Quick start

Prerequisites

Whether you’re using Windows, OS X, or Linux, you can follow this example by using either an IDE and its build tools, or by using the the .NET Core SDK command line tools.

First, make sure you have installed the gRPC C# prerequisites. You will also need Git to download the sample code.

Download the example

You’ll need a local copy of the example code to work through this quick start. Download the example code from our GitHub repository (the following command clones the entire repository, but you just need the examples for this quick start and other tutorials):

# Clone the repository to get the example code:
$ git clone -b v1.42.0 https://github.com/grpc/grpc
$ cd grpc

This document will walk you through the “Hello World” example. The projects and source files can be found in the examples/csharp/Helloworld directory.

The example in this walkthrough already adds the necessary dependencies for you (Grpc, Grpc.Tools and Google.Protobuf NuGet packages).

Build the example

Using Visual Studio (or Visual Studio for Mac)

• Open the solution Greeter.sln with Visual Studio
• Build the solution

Using .NET Core SDK from the command line

From the examples/csharp/Helloworld directory:

> dotnet build Greeter.sln

Run a gRPC application

From the examples/csharp/Helloworld directory:

• Run the server:

  > cd GreeterServer
  > dotnet run -f netcoreapp2.1
  

• From another terminal, run the client:

  > cd GreeterClient
  > dotnet run -f netcoreapp2.1
  

Congratulations! You’ve just run a client-server application with gRPC.

Update the gRPC service

Now let’s look at how to update the application with an extra method on the server for the client to call. Our gRPC service is defined using protocol buffers; you can find out lots more about how to define a service in a .proto file in Basics tutorial. For now all you need to know is that both the server and the client “stub” have a SayHello RPC method that takes a HelloRequest parameter from the client and returns a HelloResponse from the server, and that this method is defined like this:

// The greeting service definition.
service Greeter {
  // Sends a greeting
  rpc SayHello (HelloRequest) returns (HelloReply) {}
}

// The request message containing the user's name.
message HelloRequest {
  string name = 1;
}

// The response message containing the greetings
message HelloReply {
  string message = 1;
}

Let’s update this so that the Greeter service has two methods. Edit examples/protos/helloworld.proto and update it with a new SayHelloAgain method, with the same request and response types:

// The greeting service definition.
service Greeter {
  // Sends a greeting
  rpc SayHello (HelloRequest) returns (HelloReply) {}
  // Sends another greeting
  rpc SayHelloAgain (HelloRequest) returns (HelloReply) {}
}

// The request message containing the user's name.
message HelloRequest {
  string name = 1;
}

// The response message containing the greetings
message HelloReply {
  string message = 1;
}

Remember to save the file!

Generate gRPC code

Next we need to update the gRPC code used by our application to use the new service definition.

The Grpc.Tools NuGet package contains the protoc and protobuf C# plugin binaries needed to generate the code. Starting from version 1.17 the package also integrates with MSBuild to provide automatic C# code generation from .proto files.

This example project already depends on the Grpc.Tools.1.42.0 NuGet package so just re-building the solution is enough to regenerate the code from our modified .proto file.

You can rebuild just like we first built the original example by running dotnet build Greeter.sln or by clicking “Build” in Visual Studio.

The build regenerates the following files under the Greeter/obj/Debug/TARGET_FRAMEWORK directory:

• Helloworld.cs contains all the protocol buffer code to populate, serialize, and retrieve our request and response message types
• HelloworldGrpc.cs provides generated client and server classes, including:
  • an abstract class Greeter.GreeterBase to inherit from when defining Greeter service implementations
  • a class Greeter.GreeterClient that can be used to access remote Greeter instances

Update and run the application

We now have new generated server and client code, but we still need to implement and call the new method in the human-written parts of our example application.

Update the server

With the Greeter.sln open in your IDE, open GreeterServer/Program.cs. Implement the new method by editing the GreeterImpl class like this:

class GreeterImpl : Greeter.GreeterBase
{
    // Server side handler of the SayHello RPC
    public override Task<HelloReply> SayHello(HelloRequest request, ServerCallContext context)
    {
        return Task.FromResult(new HelloReply { Message = "Hello " + request.Name });
    }

    // Server side handler for the SayHelloAgain RPC
    public override Task<HelloReply> SayHelloAgain(HelloRequest request, ServerCallContext context)
    {
        return Task.FromResult(new HelloReply { Message = "Hello again " + request.Name });
    }
}

Update the client

With the same Greeter.sln open in your IDE, open GreeterClient/Program.cs. Call the new method like this:

public static void Main(string[] args)
{
    Channel channel = new Channel("127.0.0.1:50051", ChannelCredentials.Insecure);

    var client = new Greeter.GreeterClient(channel);
    String user = "you";

    var reply = client.SayHello(new HelloRequest { Name = user });
    Console.WriteLine("Greeting: " + reply.Message);

    var secondReply = client.SayHelloAgain(new HelloRequest { Name = user });
    Console.WriteLine("Greeting: " + secondReply.Message);

    channel.ShutdownAsync().Wait();
    Console.WriteLine("Press any key to exit...");
    Console.ReadKey();
}

Rebuild the modified example

Rebuild the newly modified example just like we first built the original example by running dotnet build Greeter.sln or by clicking “Build” in Visual Studio.

Run!

Just like we did before, from the examples/csharp/Helloworld directory:

1. Run the server:

   > cd GreeterServer
   > dotnet run -f netcoreapp2.1
   

2. From another terminal, run the client:

   > cd GreeterClient
   > dotnet run -f netcoreapp2.1
   

What’s next

• Learn how gRPC works in Introduction to gRPC and Core concepts.
• Work through the Basics tutorial
• Explore the API reference.