OData on .Net Core doesn't return the right results on $select

Question

I've added OData to my WebAPI project.

Versions:

1. Core 3.1
2. OData 7.3.0 (beta version in order to work with Core 3.x)
3. EF Core 3.1.0

Here is my startup.cs

public class Startup
{
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddDbContext<Models.Contexts.EntityContext>(opts => opts.UseSqlServer(Configuration["ConnectionString:MailBackup"]));
        services.AddControllers();
        services.AddMvc(options =>
        {
            options.EnableEndpointRouting = false;
        }).SetCompatibilityVersion(Microsoft.AspNetCore.Mvc.CompatibilityVersion.Version_3_0);

        services.AddOData();
    }

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        app.UseMvc(routeBuilder =>
        {
            routeBuilder.EnableDependencyInjection();
            routeBuilder.Expand().Select().OrderBy().Filter();
        });

        app.UseHttpsRedirection();
        app.UseAuthorization();

    }
}

And the controller is:

[EnableQuery()]
[HttpGet]
[Route("GetAll")]
public IQueryable<Models.EmailMessage> GetAll()
{    
    return this._context.EmailMessages;
}

The APIs are working fine, but when I try to add some OData action like $select I get the following and not the expected results:

{
    "instance": null,
    "container": {},
    "modelID": "529e8054-04c4-4729-aa91-d7eaf67a55d0",
    "untypedInstance": null,
    "instanceType": null,
    "useInstanceForProperties": false
},
{
    "instance": null,
    "container": {},
    "modelID": "529e8054-04c4-4729-aa91-d7eaf67a55d0",
    "untypedInstance": null,
    "instanceType": null,
    "useInstanceForProperties": false
},

Answer 1

I had the same problem. This solved the problem for me. Perhaps odata is not fully compatible with the new JSON serializer in Asp.Net 3.1. I don't know.

services.AddControllers(mvcOptions =>
           mvcOptions.EnableEndpointRouting = false)
       .AddNewtonsoftJson();