The Ultimate Guide to gRPC in ASP.NET Core/

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Protobuf as the Communication Protocol of gRPC

Protobuf as the Communication Protocol of gRPC

Learn about the basic file structure of Protobuf and how to translate it into C#.

We'll cover the following...

So far, we've had a look at the basic structure of gRPC client and server on .NET. Both of these applications share the same Protobuf file. This is the file that defines the schema used by Protobuf serializer to construct the messages exchanged between two applications.

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In this lesson, we'll delve deeper into the structure of this messaging format. We'll start by looking closely at the Protobuf file we've already used.

Basic Protobuf file structure

To recap, the Protobuf file that both the client and server have been using has the following content:

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syntax = "proto3";
option csharp_namespace = "BasicGrpcService";
package basic_grpc_service;
service Chatbot {
  rpc SendMessage (ChatRequest) returns (ChatReply);
}
message ChatRequest {
  string name = 1;
  string message = 2;
}
message ChatReply {
  string message = 1;
}

Let's go through this line by line to see what it does. The first statement that we see inside is syntax = "proto". This statement explicitly tells us that we're using version three of Protobuf. The previous version, proto2, is also available. However, there are some breaking changes between the versions. Since version three is the most recent, it's better to use it. Version one, on the other hand, is unavailable, because it existed before the gRPC framework was open-sourced. Then, we have the following statement on line 3:

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option csharp_namespace = "BasicGrpcService";

The option keyword indicates that it's one of the custom options available in Protobuf. The csharp_namespace option is only applicable to C# services, and it defines the namespace of the classes that are auto-generated based on the information in this Protobuf file. ...