Minimal + protobuf

Minimal-protobuf.cs

using Microsoft.AspNetCore.Http.Features;
using Microsoft.AspNetCore.WebUtilities;
using ProtoBuf;

var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();

app.MapGet("/", () => "POST a protobuf message to the /");
app.MapPost("/", (Proto<Person> p) => Results.Extensions.Protobuf(p.Item))
    .Accepts<Person>("application/protobuf");

app.Run();


[ProtoContract]
class Person
{
    [ProtoMember(1)]
    public string? Name { get; set; }
}

// Input
public struct Proto<T>
{
    public Proto(T item)
    {
        Item = item;
    }

    public T Item { get; }

    public static async ValueTask<Proto<T>> BindAsync(HttpContext context)
    {
        // TODO: Check the content type?

        // Unforutnately this serializer doesn't support async IO, we can buffer or we can allow sync IO
        // this can cause performance problems for bigger payloads to buffering might be more appropriate.
        // context.Features.Get<IHttpBodyControlFeature>()!.AllowSynchronousIO = true;

        context.Request.EnableBuffering();
        await context.Request.Body.DrainAsync(context.RequestAborted);
        context.Request.Body.Position = 0;

        var item = Serializer.Deserialize<T>(context.Request.Body);

        return new(item);
    }
}

// Output
public static class SerializerResultExtensions
{
    public static IResult Protobuf<T>(this IResultExtensions _, T obj)
    {
        return new ProtobufResult<T>(obj);
    }

    private class ProtobufResult<T> : IResult
    {
        private readonly T _item;
        public ProtobufResult(T item)
        {
            _item = item;
        }

        public Task ExecuteAsync(HttpContext httpContext)
        {
            httpContext.Response.ContentType = "application/protobuf";

            // Unforutnately this serializer doesn't support async IO, we can buffer or we can allow sync IO
            // this can cause performance problems for bigger payloads to buffering might be more appropriate.

            httpContext.Features.Get<IHttpBodyControlFeature>()!.AllowSynchronousIO = true;
            Serializer.Serialize(httpContext.Response.Body, _item);
            return Task.CompletedTask;
        }
    }
}