angular 4 + WebApi

Good morning,

I'm trying to show the objects obtained in the get request from the browser's console from angular test.service.ts:

   getTestValues_Get() :Observable<Itest []>{
  return this._http.get(this.url)
        .map(response => <Itest[]> response.json());  }

the call from the test.component.ts component:

ngOnInit() {             
         this._TestService.getSettings_Get()
         .subscribe(( test: ITest []) => {
              this.test= test;
             console.log("Array ->:" + this.test)
         });}

From the WebApi returns this in ValuesController.cs.

   [HttpGet]
    public Setting Get()
    {
        using (Entities EntityDB= new Entities())
        {
           return EntityDB.Settings.FirstOrDefault(e=>e.TestId == 1);
        }
    }

When I run it I get this error:

  

The 'ObjectContent'1' type failed to serialize the response body for   content type 'application / json

I have also added in WebApiConfig.cs:

        config.Formatters.Remove(config.Formatters.XmlFormatter);
        config.Formatters.Add(config.Formatters.JsonFormatter);

        var json = config.Formatters.JsonFormatter;
        json.SerializerSettings.PreserveReferencesHandling = Newtonsoft.Json.PreserveReferencesHandling.Objects;
        config.Formatters.Remove(config.Formatters.XmlFormatter);

Any idea where the problem might be?

Greetings,