如何使用protobuf-net.Reflection解析.proto文件和读取自定义消息选项？

Install-Package protobuf-net.Reflection

syntax = "proto3";

import "google/protobuf/descriptor.proto";

extend google.protobuf.MessageOptions {
  optional string my_custom_option = 50000;
}

message MyMessage {
  option (my_custom_option) = "This is a custom option value";
  int32 id = 1;
  string name = 2;
}

using System;
using System.IO;
using Google.Protobuf;
using Google.Protobuf.Reflection;
using ProtoBuf;
using ProtoBuf.Meta;

public class ProtobufReflectionExample
{
    public static void Main()
    {
        // 加载 .proto 文件内容
        string protoContent = File.ReadAllText("path/to/your/file.proto");

        // 创建一个 RuntimeTypeModel 实例
        var model = RuntimeTypeModel.Default;

        // 使用 Protobuf 编译器解析 .proto 文件
        var fileDescriptorSet = DescriptorPool.Default.FromProto(protoContent);
        foreach (var fileDescriptor in fileDescriptorSet.File)
        {
            foreach (var messageType in fileDescriptor.MessageType)
            {
                // 注册消息类型到模型中
                model.Add(messageType.Name, messageType.FullName);
            }
        }

        // 创建消息实例
        var message = new MyMessage { Id = 1, Name = "Test" };

        // 序列化和反序列化消息（仅用于演示）
        byte[] bytes;
        using (var stream = new MemoryStream())
        {
            Serializer.Serialize(stream, message);
            bytes = stream.ToArray();
        }

        using (var stream = new MemoryStream(bytes))
        {
            var deserializedMessage = Serializer.Deserialize<MyMessage>(stream);
            Console.WriteLine($"Deserialized Message: {deserializedMessage.Id}, {deserializedMessage.Name}");
        }

        // 读取自定义消息选项
        var typeModel = model[typeModel.GetMessageType(typeof(MyMessage))];
        var fieldInfo = typeModel.Fields[0];
        var options = fieldInfo.Options;
        if (options.HasExtension(MyCustomOptions.my_custom_option))
        {
            var customOptionValue = options.GetExtension(MyCustomOptions.my_custom_option);
            Console.WriteLine($"Custom Option Value: {customOptionValue}");
        }
    }
}

// 定义自定义选项的静态类
public static class MyCustomOptions
{
    public const int MyCustomOptionFieldNumber = 50000;
    [ProtoMember(MyCustomOptionFieldNumber)]
    public static readonly GeneratedExtension<MessageOptions, string> my_custom_option =
        new GeneratedExtension<MessageOptions, string>(null, ExtensionFlags.None);
}