Build gRPC Client with .NET Core

In the previous posts on the series about gRPC, we have seen how to build a simple gRPC request/reply service and a gRPC server streaming service by using .NET Core and the new grpc-dotnet, the managed library entirely written in C#. Now it’s the time to create and build a .NET gRPC client. And it’s really easy to do.

Create and configure our client project

First of all, we need to create a client project. For the purpose of this article, a simple console project will be enough. So, you can open the terminal, go to your preferred folder and execute the following command:

dotnet new console -o GrpcClient

Then go to the folder just created and add the necessary reference with the following commands:

dotnet add package Google.Protobuf
dotnet add package Grpc.Net.Client
dotnet add package Grpc.Tools

Now, we can create the bookshelf.proto file (full code available on my github repository:

syntax = "proto3";

option csharp_namespace = "BookshelfService";

package BookshelfService;

// The bookshelf service definition.
service BookService {
  // Get full list of books
  rpc GetAllBooks (AllBooksRequest) returns (stream AllBooksReply);
  // Save a Book
  rpc Save (NewBookRequest) returns (NewBookReply);
}

// The request message containing the book's title and description.
message AllBooksRequest {
  int32 itemsPerPage = 1;
}

// The request message containing the book's title and description.
message AllBooksReply {
  repeated Book Books = 1;
}

message Book {
  string title = 1;
  string description = 2;
}

// The request message containing the book's title and description.
message NewBookRequest {
  string title = 1;
  string description = 2;
}

// The response message containing the book id.
message NewBookReply {
  string id = 1;
}

We can then add the just created file to the project by using dotnet-grpc CLI. If you haven’t installed yet, execute the following command:

dotnet tool install -g dotnet-grpc

then add the bookshelf.proto to the client project:

dotnet grpc add-file bookshelf.proto --services Client

Finally, be sure to set the right GrpcService value of the Protobuf element in your .csproj file:

You can set the GrpcService attribute to decide the kind of grpc generated code. The accepted values are: Both, Client, Default, None, Server.

<ItemGroup>
  <Protobuf Include="..\Protos\bookshelf.proto" GrpcServices="Client" />
</ItemGroup>

Let’s start coding

Calling a Grpc Service is a very simple operation. Just create the channel, connect to the service endpoint, and then pass it to the generated client as a constructor parameter. Now you can use the client instance to invoke the service methods:

using (var channel = GrpcChannel.ForAddress("http://localhost:5000"))
{
    var request = new NewBookRequest();
    request.Title = "1984";
    request.Description = "A George Orwell novel";

    var client =  new BookService.BookServiceClient(channel);
    client.Save(request);
}

NOTE: if you are on macOs, HTTP/2 on TLS is still not supported, so you need to deactivate it by using the following instruction before connect to the service: AppContext.SetSwitch("System.Net.Http.SocketsHttpHandler.Http2UnencryptedSupport", true);

Enjoy!

check full code on github