从Angular5进行POST时WCF对象为null

Question

我们正在尝试发布到WCF REST方法。我们可以使用SoapUI，Postman和YARC成功地进行POST，但是当我们在Angular 5中尝试时，我收到的是NULL对象。

客户代码：

    const headers: any =  {'Content-Type': 'application/json'};
    return this.ajax.request<any>({
        url: url,
        method: method (POST),
        headers: headers,
        options: {
            body: JSON.stringify(req.body)
        }
        });
    }

    public request<T>(req: AjaxRequest): Observable<HttpEvent> {
        return this.http.request<T>(req.method, req.url, req.options)
    }

    //this.http = HttpClient

    // Component
    public onNext(event: any): void {
        this._saveInfo(getInsertDmgReqPayload({
            data: event.value,
            dmgInfo: this.responses['dmg'],
            emailId: this.util.getQueryStringValue('uname')
        }));

        this.util.navigate('education');
    }

    private _saveInfo(data: any): void {
        this.appraisal.request('saveDmgInfo', null, {body: data})
        .subscribe(v => {
            console.log(v);
        });
    }

服务器端逻辑：

// WCF Interface definition
    [OperationContract]
    [WebInvoke(Method = "POST", RequestFormat = WebMessageFormat.Json, BodyStyle = WebMessageBodyStyle.Bare)]
    Result InsertDemographicInfo(Demographic d);

    // Service code
    public Result InsertDemographicInfo(Demographic d) // The Demographic object is null when posting from Angular
    {
        Result result = new Result();
        try
        {
            DemographicFactory.InsertDemographicInfo(d);
            result.Status = "Success";
        }
        catch (Exception ex)
        {
            result.Status = "Fail";
            result.Message = ex.Message;
        }
        return result;
    }

我已经尝试过用here和here来命名Angular中的参数，并且该参数始终为null。请帮忙？我的头发足够白。