"no body provided" response when POSTing to a minimal endpoint

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I'm experimenting with converting some simple controller methods to using endpoint routing on the latest RC of aspnet core 6. The controller works fine, and it looks like this:

[HttpPost]
public async Task<IActionResult> CreateUser(NewUserRequest newUser)
{
    /* do stuff with newUser */
    /* return CreatedAtRoute(...); */
}

I've tried converting to using IEndpointRouteBuilder, like so:

endpoints.MapPost("/api/user/test",
    (NewUserRequest request) =>
    {
        /* same thing as controller method */
    });

// prints error to the log:
// Implicit body inferred for parameter "request" but no body was provided. Did you mean to use a Service instead?

I'm using the exact same test request (through Postman, usually), so I know it's not the client's problem. What's more, if I just take an HttpRequest parameter, I can read the body into a json blob.

endpoints.MapPost("api/user/test2",
    async (HttpRequest request) =>
    {
        using (var sr = new StreamReader(request.BodyReader.AsStream()))
        {
            var body = await sr.ReadToEndAsync();

            /* body is valid json here */
        }
    });

I'm really at a loss here, especially since it works in some cases, but not when I'm binding a type to one of the minimal endpoints.

.net-6.0 asp.net-core endpoint
1 Answers

The syntax you used is available in Minimal APIs first introduced in ASP.NET Core 6 Preview 4. At that time it wasn't possible to bind to specific objects yet. It's not related to Endpoint routing which was added in ASP.NET Core 3.1.

If you create a new "empty" web app with dotnet new web you get:

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

app.MapGet("/", () => "Hello World!");
app.Run();

This is using endpoint routing through the new WebApplication class. To add the POST endpoint you can use :

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

app.MapGet("/", () => "Hello World!");
app.MapPost("/api/user/test",(NewUserRequest request) =>
    {
        Console.WriteLine(request.Name);
        return request;
        /* same thing as controller method */
    });

app.Run();

class NewUserRequest
{
    public string Name{get;set;}
}

Additional classes and methods must be defined at the end of the file.

Testing this with curl :

curl -X POST https://localhost:7153/api/user/test -d '{ "Name":"A"}' -H 'Content-Type: application/json' -v

Logs A in the service's console and returns

{"name":"A"}%

to the client.

The reason you get this error :

Implicit body inferred for parameter "request" but no body was provided. Did you mean to use a Service instead?

Is that in ASP.NET Core 6 Preview 6 it became possible to inject services without using the [FromServices] attribute. In the following code, the DbContext is injected:

app.MapGet("/todos", async (TodoDbContext db) =>
{
    return await db.Todos.ToListAsync();
});
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