async wcf服务返回null

Question

您好我正在创建一个异步WCF服务并在HTML应用程序中使用它，但每次我从服务中获取null。我是异步方法的新手，所以请指导我，我在这里分享我的代码：

Service.cs

public static async Task<string> GetTJSON()
{
 string responseData = string.Empty;
        using (var httpClient = new HttpClient())
        {
            using (var response = await httpClient.GetAsync("http://api.xyz.com/json/feeds?system=apios").ConfigureAwait(false))
           {
                responseData = await response.Content.ReadAsStringAsync();
                return responseData;
            }
        }
}

public async Task<string> getJ()
    {
        var json = await GetTJSON();
        return json.ToString();
}

Iservice.cs

[OperationContract]
[WebInvoke(Method = "GET", UriTemplate = "GetJsonNet1", ResponseFormat = WebMessageFormat.Json, RequestFormat = WebMessageFormat.Json, BodyStyle = WebMessageBodyStyle.Wrapped)]
Task<string> getJ();

HTML / Jquery的

var GetJsonNet = function () {
        $.ajax({
            type: "GET",
            url: "http://localhost:59835/Service1.svc/GetJsonNet1",
            contentType: "application/json;charset=utf-8",
            dataType: "json",
            success: function (data) {
                var result = data.GetEmployeeJSONResult;
                console.log(result);
                var obj = $.parseJSON(result);
                alert('s:' + obj);
            },
            error: function (xhr) {
                alert('e:'+xhr.responseText);
            }
        });
    }