Mvc: Web API doesnt work when getting data from EF Core using .Include

[Cae2]

Hello guys,
I setted up an API to return data from my database.

Everything went fine in a case like this:

    [HttpGet()]
    public IEnumerable<table1> table1()
    {
        var a = _context.table1.Take(10).ToList();
        var b = _context.table1.Include(i => i.table2).Take(10).ToList();
        return a;
    }

but if I set return to "b" the API stops (when debugging in VS2017, both returns valid data).

checking with Swagger (or Postman) it says: "no content" with a response code 0.

If I try to check the API url direct from browser it shows just 1 record (debugging shows correctly the 10 records).

not sure if I made myself clear, I can provide more data/screenshots if needed.

Thanks

[stefannikolei]

Can you post your model classes?

[Cae2]

Hi, Im sending attached. Note that those models were generated automatically by Scaffold-DbContext.

also I was checking the console.log and noticed that when I use .Include, the response is:

GET http://localhost:50757/api/NotasFiscais/ net::ERR_CONNECTION_RESET
XHR failed loading: GET "http://localhost:50757/api/NotasFiscais/".
EXCEPTION: Response with status: 0 for URL: null

also if I tried direct with curl I get:
PS C:\Users\flavi> curl 'http://localhost:50757/api/NotasFiscais'
curl : Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host.
At line:1 char:1
+ curl 'http://localhost:50757/api/NotasFiscais'

NotasFiscais.txt
Fornecedores.txt

[Eilon]

@Cae2 I'm guessing that an exception is being thrown on the server. Have you tried running it with the debugger to see if that's the case?

[Cae2]

@Eilon There is no exception on server, it seems that the http connection is suddenly dropping.

I noticed that running the API uri on chrome, for example in the first attempt:

and after a F5:

in the second attempt the result was more complete (it seems that at least 1 record is complete, but the connection was dropped with "net::ERR_CONNECTION_RESET" before receive another 9 for example)

[Eilon]

@cesarbs any idea on what this could be?

[Cae2]

@Eilon , Running via powershell finally shows me an error:

it seems that is related to:
https://github.com/aspnet/IISIntegration/issues/285

but there is a lot of info there, will need to take a more deeply look, not sure if its still "fixed"

[Cae2]

thats it, edited Startup.cs and change:

services.AddMvc()
to
services.AddMvc().AddJsonOptions(x => x.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore);

did the trick and now its working (just didnt understood if its an error or working as intended)

thanks

[Eilon]

Yeah by default Json.NET will throw if you try to serialize circular references (because it's impossible 😄 ).

The reason the connection is reset is that the exception happens while the response has already started writing, and there's no way to un-write data in a response, so this is the only option to end the request.

[vishalps868]

@Cae2 - Thanks a ton!! Your solution save my day!! :)

[jkevincgo]

@Cae2 Thanks, this worked for me too. :)

[mootinator]

I had an _intermittent_ problem with this error, apparently there's a race condition in older versions of the .NET Core Windows Server Hosting bundle where the connection will sometimes/often close normally before terminating this way. The issue was blocking us from upgrading and getting to be extremely annoying for users.

All because I wrote this in front of a property: /* TODO: This breaks serialization */
Instead of this: [JsonIgnore]

Thanks for the help tracking that down.