How to stop self-referencing loop in .Net Core Web API?

ReferenceLoopHandling.Ignore “hides” the problem, not solves it. What you really need to be doing is building layers. Create domain objects to sit on top of your entities and wrap them in some sort of service/business layer. Look up the repository pattern and apply that if it helps. You’ll need to map between your entities and domain objects, and this gives you the chance to fit in some sort of mapper (automapper) and validation layer..

If your domain objects and entities are exactly the same, then you need to think more about what your doing.

For example: Do your entities have soft deletes? (IsDeleted) flag? If so, this doesn’t necessarily need to go back to the client over the web, so that’s a perfect example of where they would be different.

Either way, the answer is not to override it in JSON, it’s to change your architecture..

Okay... I finally found some reference material on this. The solution is:

public void ConfigureServices(IServiceCollection services)
{
    ...

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

    ...
}

I got this from here

If you are using ASP.NET Core 3.0, and experience that problem please install the NuGET package: Microsoft.AspNetCore.Mvc.NewtonsoftJson 3.0.0.

To replace the new System.Text.Json which does not yet have the Reference Loop Handling do this in the Startup.cs, make sure that in the ConfigureServices, is included:

If using the latest .Net Core 3.0 way:

services.AddControllers().AddNewtonsoftJson(options =>
{
    options.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
});

or the old way:

services.AddMvc(option => option.EnableEndpointRouting = false)
       .AddNewtonsoftJson(options => 
                 options.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore)
       .SetCompatibilityVersion(CompatibilityVersion.Version_3_0);