Lesson 18 of 40 Backend Services Advanced 50 min

gRPC & Protobuf Services

In this lesson, you will learn how gRPC uses Protocol Buffers for fast, strongly typed communication between services, and how Visual Studio 2026 helps you build and test gRPC services in .NET.

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What you will learn

How gRPC differs from REST APIs
How Protobuf contracts define messages and services
How gRPC services are implemented in .NET
How clients call gRPC endpoints
When gRPC is a strong choice for service-to-service communication

Why this matters: gRPC is efficient, strongly typed, and especially useful in internal systems and microservices.

Part 1: Defining contracts with Protobuf

Protobuf files define the structure of messages and the operations exposed by a service.

syntax = "proto3";

service Greeter {
  rpc SayHello (HelloRequest) returns (HelloReply);
}

message HelloRequest {
  string name = 1;
}

message HelloReply {
  string message = 1;
}
    

Part 2: Implementing a gRPC service

Once the contract is defined, .NET generates types that you can implement on the server.

public class GreeterService : Greeter.GreeterBase
{
    public override Task SayHello(HelloRequest request, ServerCallContext context)
    {
        return Task.FromResult(new HelloReply
        {
            Message = $"Hello, {request.Name}"
        });
    }
}
    

Part 3: Calling a gRPC service

gRPC clients use generated code, which gives you a strongly typed calling experience.

var channel = GrpcChannel.ForAddress("https://localhost:5001");
var client = new Greeter.GreeterClient(channel);

var reply = await client.SayHelloAsync(new HelloRequest { Name = "Dr. Liew" });
    

Part 4: When to use gRPC

Scenario	Why gRPC fits
Internal microservices	Fast and strongly typed communication
Cross-language backends	Contract-first design supports multiple platforms
Streaming data	Supports client, server, and bidirectional streaming
Public browser APIs	Usually REST is simpler for direct browser access

Summary

In this lesson, you learned how gRPC and Protobuf create efficient, strongly typed service contracts and how .NET implements and consumes those services.

In the next lesson, you will explore background services and worker processes.