在 asp.net MVC 控制器中调用异步外部 Web 服务

Question

在 Asp.net MVC 控制器（GET 方法）中，我正在调用外部 Web 服务 - 用于 IP 的地理位置 - 返回 IP 位置的 json 数据。如何使调用异步，因此堆栈可以在等待服务响应时继续。 GEO IP 请求完成后，我希望能够对数据库进行更新。这是当前的同步代码：

public ActionResult SelectFacility(int franchiseId, Guid? coachLoggingTimeStampId)
{
    //...
    string responseFromServer = Helpers.GetLocationByIPAddress(userIpAddress);

    HomeModels.GeoLocationModel myojb = new HomeModels.GeoLocationModel();

    if (!String.IsNullOrEmpty(responseFromServer))
    {
        JavaScriptSerializer js = new JavaScriptSerializer();
        myojb = (HomeModels.GeoLocationModel)js.Deserialize(responseFromServer, typeof(HomeModels.GeoLocationModel));

    }
    //...
}
public static string GetLocationByIPAddress(string ipAddress)
{
    Stream resStream = null;
    string responseFromServer = "";
    try
    {
        string url = GeoLocationPath.FreeGeoIP + ipAddress;
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
        request.Method = "GET";
        HttpWebResponse response = (HttpWebResponse)request.GetResponse();
        resStream = response.GetResponseStream();
        StreamReader reader = new StreamReader(resStream);
        responseFromServer = reader.ReadToEnd();
        return responseFromServer;
    }
    catch (Exception ex)
    {
        //TODO handle this
    }
    finally
    {
        if (null != resStream)
        {
            resStream.Flush();
            resStream.Close();
        }
    }
    return responseFromServer;
}

任何建议 - 线程，AsyncTask ？ 谢谢

Answer 1

使您的 ASP.NET MVC 控制器异步：

http://www.asp.net/mvc/tutorials/mvc-4/using-asynchronous-methods-in-aspnet-mvc-4

然后使用HttpClient.GetStringAsync 和await 其结果：

public async Task<ActionResult> SelectFacility(
    int franchiseId, Guid? coachLoggingTimeStampId)
{
    //...
    string responseFromServer = await Helpers.GetLocationByIPAddressAsync(
        userIpAddress);
    //...
}

public static async Task<string> GetLocationByIPAddress(string ipAddress)
{
    using (var httpClient = new HttpClient())
        return await httpClient.GetStringAsync(
            GeoLocationPath.FreeGeoIP + ipAddress);
}