C# NodeInvocationException:JSON输入意外结束

我正在使用Asp.Net内核和Angular 4作为前端

我打电话给ProjectRoleService如下

import { Injectable, Inject } from '@angular/core';
import { Observable } from 'rxjs/Observable';
import { Http } from '@angular/http';
import 'rxjs/Rx';

@Injectable()
export class ProjectRoleService {   
    _serverURL: string;
    constructor(private _http: Http) {
        this._serverURL = "http://localhost:8080/api";
    }
    getMenuDetails(roleName: string) {
        let _url = this._serverURL + "/Menu/GetMenuDetails?roleName=" + roleName;

        return new Promise((resolve, reject) => {
            this._http.get(_url)
                .map(res => res.json())
                .catch((error: any) => {
                    console.error(error);
                    reject(error);
                    return Observable.throw(error.json().error || 'Server error');
                })
                .subscribe((data) => {
                    resolve(data);
                });
        });
    }
}  

public class MenuController : ApiController
    {
        /// <summary>  
        /// Get Menu Details by logged in user role  
        /// </summary>  
        /// <param name="email ID"></param>  
        /// <returns></returns>  
        [Microsoft.AspNetCore.Mvc.HttpGet]
        public HttpResponseMessage GetMenuDetails(string roleName)
        {
            HttpResponseMessage httpResponseMessage = null;

            try
            {
                httpResponseMessage = Request.CreateResponse(new Menu().GetMenuDetails(roleName));
            }
            catch (Exception ex)
            {
                throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError)
                {
                    Content = new StringContent(ex.Message),
                    ReasonPhrase = "Warning"
                });
            }
            return httpResponseMessage;
        }
    }

我已将本地主机URL配置为

http://localhost:8080/

并将服务器URL设置为

this.\u serverURL=”http://localhost:8080/api";

MenuController
类如下

import { Injectable, Inject } from '@angular/core';
import { Observable } from 'rxjs/Observable';
import { Http } from '@angular/http';
import 'rxjs/Rx';

@Injectable()
export class ProjectRoleService {   
    _serverURL: string;
    constructor(private _http: Http) {
        this._serverURL = "http://localhost:8080/api";
    }
    getMenuDetails(roleName: string) {
        let _url = this._serverURL + "/Menu/GetMenuDetails?roleName=" + roleName;

        return new Promise((resolve, reject) => {
            this._http.get(_url)
                .map(res => res.json())
                .catch((error: any) => {
                    console.error(error);
                    reject(error);
                    return Observable.throw(error.json().error || 'Server error');
                })
                .subscribe((data) => {
                    resolve(data);
                });
        });
    }
}  

public class MenuController : ApiController
    {
        /// <summary>  
        /// Get Menu Details by logged in user role  
        /// </summary>  
        /// <param name="email ID"></param>  
        /// <returns></returns>  
        [Microsoft.AspNetCore.Mvc.HttpGet]
        public HttpResponseMessage GetMenuDetails(string roleName)
        {
            HttpResponseMessage httpResponseMessage = null;

            try
            {
                httpResponseMessage = Request.CreateResponse(new Menu().GetMenuDetails(roleName));
            }
            catch (Exception ex)
            {
                throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError)
                {
                    Content = new StringContent(ex.Message),
                    ReasonPhrase = "Warning"
                });
            }
            return httpResponseMessage;
        }
    }

public类菜单控制器：ApiController
{
///   
///通过登录用户角色获取菜单详细信息
///   
///   
///   
[Microsoft.AspNetCore.Mvc.HttpGet]
公共HttpResponseMessageGetMenuDetails（字符串roleName）
{
HttpResponseMessage HttpResponseMessage=null；
尝试
{
httpResponseMessage=Request.CreateResponse（新菜单（）.GetMenuDetails（roleName））；
}
捕获（例外情况除外）
{
抛出新的HttpResponseException（新的HttpResponseMessage（HttpStatusCode.InternalServerError）
{
内容=新的字符串内容（例如消息），
ReasonPhrase=“警告”
});
}
返回httpResponseMessage；
}
}

在IISExpress上运行时，我得到如下错误。我在项目设置中仅为此启用了匿名

    NodeInvocationException: Unexpected end of JSON input
    SyntaxError: Unexpected end of JSON input
    at JSON.parse (<anonymous>)
    at Response.module.exports.Body.json (E:\AngularProject\NodeUI\ClientApp\dist\vendor.js:71887:25)
    at CatchSubscriber.selector (E:\AngularProject\NodeUI\ClientApp\dist\main-server.js:19325:96)
    at CatchSubscriber.module.exports.CatchSubscriber.error (E:\AngularProject\NodeUI\ClientApp\dist\vendor.js:91048:31)
    at MapSubscriber.module.exports.Subscriber._error (E:\AngularProject\NodeUI\ClientApp\dist\vendor.js:10724:26)
    at MapSubscriber.module.exports.Subscriber.error (E:\AngularProject\NodeUI\ClientApp\dist\vendor.js:10698:18)
    at ZoneTask.onComplete [as callback]    (E:\AngularProject\NodeUI\ClientApp\dist\main-server.js:4454:30)
    at ZoneDelegate.module.exports.ZoneDelegate.invokeTask (E:\AngularProject\NodeUI\ClientApp\dist\vendor.js:85819:31)
    at Object.onInvokeTask (E:\AngularProject\NodeUI\ClientApp\dist\vendor.js:14821:37)
    at ZoneDelegate.module.exports.ZoneDelegate.invokeTask (E:\AngularProject\NodeUI\ClientApp\dist\vendor.js:85818:36)

NodeInvocationException:JSON输入意外结束
SyntaxError:JSON输入意外结束
在JSON.parse（）处
位于Response.module.exports.Body.json（E:\AngularProject\NodeUI\ClientApp\dist\vendor.js:71887:25）
在CatchSubscriber.selector（E:\AngularProject\NodeUI\ClientApp\dist\main server.js:19325:96）
位于CatchSubscriber.module.exports.CatchSubscriber.error（E:\AngularProject\NodeUI\ClientApp\dist\vendor.js:91048:31）
在MapSubscriber.module.exports.Subscriber.\u错误（E:\AngularProject\NodeUI\ClientApp\dist\vendor.js:10724:26）
在MapSubscriber.module.exports.Subscriber.error（E:\AngularProject\NodeUI\ClientApp\dist\vendor.js:10698:18）
在ZoneTask.onComplete[作为回调]（E:\AngularProject\NodeUI\ClientApp\dist\main server.js:4454:30）
位于ZoneDelegate.module.exports.ZoneDelegate.invokeTask（E:\AngularProject\NodeUI\ClientApp\dist\vendor.js:85819:31）
位于Object.onInvokeTask（E:\AngularProject\NodeUI\ClientApp\dist\vendor.js:14821:37）
位于ZoneDelegate.module.exports.ZoneDelegate.invokeTask（E:\AngularProject\NodeUI\ClientApp\dist\vendor.js:85818:36）

当我尝试运行项目时，就会发生这种情况

我怀疑问题在于调用服务器URL
我的res.json（）足够好吗
我在这里遗漏了什么？
“JSON输入的意外结束”表示出现了一些格式错误的JSON。您应该查看服务器响应并确保它实际上是JSON。当出现异常时，您的响应中没有JSON。
.JSON（）
也会返回一个承诺。我如何检查它是否返回JSON数据？是否有条件检查内容类型？