Object deserialization fails POST in Asp Net Core MVC Controller

Question

I created an API app without the full blown MVC template. However, a POST request with body always fails with Internal Server Error.

I followed the exact same steps here for a stateful service:

I created a project with the Stateful Service template in Visual Studio. I added a Kestrel listener as described here:

protected override IEnumerable<ServiceReplicaListener> CreateServiceReplicaListeners()
{
    return new ServiceReplicaListener[]
    {
        new ServiceReplicaListener(serviceContext =>
            new KestrelCommunicationListener(serviceContext, (url, listener) =>
                new WebHostBuilder()
                    .UseKestrel()
                    .ConfigureServices(
                         services => services
                             .AddSingleton<StatefulServiceContext>(serviceContext)
                             .AddSingleton<IReliableStateManager>(this.StateManager))
                    .UseContentRoot(Directory.GetCurrentDirectory())
                    .UseServiceFabricIntegration(listener, ServiceFabricIntegrationOptions.UseUniqueServiceUrl)
                    .UseStartup<Startup>()
                    .UseUrls(url)
                    .Build()
            ))
    };
}

Then, I added a Startup class and a test controller: internal class Startup { public IConfiguration Configuration { get; } public void ConfigureServices(IServiceCollection services) { services.AddMvcCore(); } public void Configure(IApplicationBuilder app, IHostingEnvironment env) { app.UseMvc(); } }

[Route("[controller]")]
[ApiController]
public class MyController : ControllerBase
{

    [HttpGet("Read1")]
    public async Task<ActionResult<string>> Read1()
    {
        return "asd";
    }
    [HttpPost("Read2")]
    public async Task<ActionResult<string>> Read2()
    {
        return "asd";
    }
    [HttpPost("Read3")]
    public async Task<ActionResult<MyOutput>> Read([FromBody]MyInput input)
    {
       
        var a = new MyOutput();
        a.Value= "asdasd";
        return a;
        
    }
}

using System.Runtime.Serialization;
[DataContract]
public class MyInput
{

    [DataMember]
    public string Value{ get; }

    public MyInput(string val)
    {
        Value= val;
    }
}

When I make a request to these 3 endpoints, the /Read1 and /Read2 requests work fine. However, /Read3 request fails with Internal Server Error on the client side and I tried to put a breakpoint into controller but for /Read3 it will never hit it. That makes me think the deserialization is not working.

I send the requests from Insomnia. A simple POST request with a content-type header set to "application/json" and JSON body:

{
    "Value": "cat"
}

What might be causing this?

Answer 1

In my case, I was missing the json formatter:

services.AddMvcCore().AddJsonFormatters();

Maybe it helps someone.