C# 将HttpWebRequest与async和Wait一起使用

我刚开始使用C#，所以请原谅我对如何使用它的无知（如果有的话）。 我有一个登录按钮，它执行以下代码

private void Login_Click(object sender, RoutedEventArgs e)
    {
        if (email_box.Text != "" && password_box.Password != "") {
            string strRegex = @"^([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}" +    @"\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([a-zA-Z0-9\-]+\" +  @".)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$";
            Regex reg = new Regex(strRegex);
            if (reg.IsMatch(email_box.Text))
            {
                ApiCall request = new ApiCall();
                request.requestData = "{\"sessions\": {\"links\":{\"user\":{\"email\":\"" + email_box.Text + "\",\"password\":\"" + password_box.Password + "\" }}}}";
                request.requestMethod = Constants.httpMethods[0];
                request.resource_url = "/sessions";
                var response = request.initialize_request();       
                //Once i get the response string, i will deserialize it here and use it to do other things, like navigate to a new page an any other neccessary things to do!
            }
            else
            {
                recover.Text = "Please provide a valid email address.";
            } 
        }
        else
        {
            recover.Text = "Email and Password cannot be Empty";
        }
    }   

该方法初始化该类，并调用初始化_请求（），该函数在内部调用GetRequestStreamCallback，该函数也调用GetResponseStreamCallback

初始化请求应该发回一个字符串，该字符串在GetResponseStreamCallBack中设置，但它似乎在最后两个方法执行之前发回一个字符串。 Soo，我读过关于async和await的文章，我也尝试过使用它们，但是Visual Studio说不能等待“方法组”，我把等待放在那里

    using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
using System.Diagnostics;
using System.Net;
using Newtonsoft.Json;
using PrintMyPic.ApiJsonObjects;
using PrintMyPic;
using System.Windows.Navigation;

namespace MyApp
{
    class ApiCall
    {
        public static string api_url = "http://myappsapiurl/api";
        public static string content_type = "application/vnd.api+json";
        public string requestData; 
        public string requestMethod; 
        public string resource_url; // the rest of the api url 
        public string requestResponse;               
    public async Task<string> initialize_request()
    {
        Debug.WriteLine("the resource used is "+ resource_url);
        System.Uri myUri = new System.Uri(api_url+resource_url);
        HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(myUri);
        request.ContentType = content_type;
        request.Method = requestMethod;
        request.Accept = content_type;
        request.BeginGetRequestStream(new AsyncCallback(await GetRequestStreamCallback), request);
        Debug.WriteLine("have we returned yet?");
       return requestResponse;
    }
    private async Task  GetRequestStreamCallback(IAsyncResult callbackResult)
    {
        Debug.WriteLine("we are in the second method");
        HttpWebRequest webrequest = (HttpWebRequest)callbackResult.AsyncState;
        Stream postStream = webrequest.EndGetRequestStream(callbackResult);           
        byte[] byteArray = Encoding.UTF8.GetBytes(requestData);
        postStream.Write(byteArray, 0, byteArray.Length);
        postStream.Close();
        webrequest.BeginGetResponse(new AsyncCallback( await GetResponsetStreamCallback), webrequest);
    }

    private void GetResponsetStreamCallback(IAsyncResult callbackResult)
    {
        Debug.WriteLine("we are in the third method");

        try
        {
            HttpWebRequest request = (HttpWebRequest)callbackResult.AsyncState;
            HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(callbackResult);
            string responseString = "";
            Stream streamResponse = response.GetResponseStream();
            StreamReader reader = new StreamReader(streamResponse);
            responseString = reader.ReadToEnd();
            streamResponse.Close();
            reader.Close();
            response.Close();
            requestResponse = responseString;
        }
        catch (Exception e)
        {
            //show user-friendly error message as well as detailed one.
            //for better UI, consider using WPToolKit's CustomMessageBox to show these
            Debug.WriteLine("something wrong happened. \nDetails: " + e.HResult.ToString());
        }
    } 

}
}

---

现在的问题是，GetResponsetStreamCallback从未启动，看起来我从未返回，因为

Debug.WriteLine（“我们返回了吗？”）永远不会执行
 < P>如Stephen Cleary所提到的，因为您正在构建Windows Phone 8，请考虑使用<代码> HTTPcli客< /代码>，而不是<代码> HttpWebRequest < /Cord>类。这背后的原因不仅仅是“容易得多”

如VS论坛所述：

HttpClient
更像是一款无头浏览器。它是一个强有力的
如果要创建多个http请求，这是一个理想的工具。对于
例如，您可以设置默认的标题和内容。以下是五大方法
它与HttpWebRequest不同：

HttpClient
实例是配置扩展、设置
默认标题、取消未完成的请求等
您可以通过单个
HttpClient
实例发出任意数量的请求
HttpClient不绑定到特定的HTTP服务器或主机；您可以使用相同的
HttpClient
实例提交任何HTTP请求

您可以从
HttpClient
派生，为特定站点或模式创建专门的客户端

HttpClient
使用新的面向任务的模式来处理异步请求，从而大大简化了管理和维护
协调多个未完成的请求
欲了解更多信息，请阅读全文并参考此

有几个例子和完整的项目展示了如何以不同的方式使用
HttpClient
，不仅可以加载字符串，还可以从JSON对象创建c对象。
不需要GetRequestStreamCallback方法异步。将其签名更改为private void GetRequestStreamCallback（IAsyncResult callbackResult）@VictorMukherjee我已经尝试过了，但仍然是'Debug.WriteLine（“我们返回了吗？”）；'在两个方法中的任何一个之前执行！另外，如果要使用异步模型.Debug.WriteLine（“我们返回了吗？”），那么您可能需要使用request.GetRequestStreamAsync；在大多数情况下，将在这两个方法之前执行，因为request.BeginGetRequestStream方法是异步执行的，但由于它不使用任何async关键字，因此不能等待任务。但是，您可以在开始eTRequestStream后使用AutoResteEvent等待initialize_请求方法，并从GetResponsetStreamCallback设置AutoResteEvent。@VictorMukherjee我已经尝试过AutoResteEvent，请参阅更新的问题！谢谢。我将调查
HttpClient
将对此给出反馈！尽管如此，我更感兴趣的是一个解决我目前状况的方案，然后是替代方案。我完全理解你的意思，只是我觉得使用过时的东西是不对的。检查：我已经转到
HttpClient
，它正在做这项工作，在多次尝试修复问题失败后，它将把代码推送到git hub并在此处共享链接。谢谢你的推荐
namespace MyApp
{
    class ApiCall
    {
        public static string api_url = "http://myappapirul/api";
        public static string content_type = "application/vnd.api+json";
        public string requestData; 
        public string requestMethod; 
        public string resource_url; // the rest of the api url 
        public string requestResponse;
        public static AutoResetEvent objAuto = new AutoResetEvent(false);       
    public string initialize_request()
    {
        Debug.WriteLine("the resource used is "+ resource_url);
        System.Uri myUri = new System.Uri(api_url+resource_url);
        HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(myUri);
        request.ContentType = content_type;
        request.Method = requestMethod;
        request.Accept = content_type;
        request.BeginGetRequestStream(new AsyncCallback(GetRequestStreamCallback), request);
        objAuto.WaitOne();
        Debug.WriteLine("have we returned yet?");
        return requestResponse;

    }
    private void  GetRequestStreamCallback(IAsyncResult callbackResult)
    {
        Debug.WriteLine("we are in the second method");
        HttpWebRequest webrequest = (HttpWebRequest)callbackResult.AsyncState;
        Stream postStream = webrequest.EndGetRequestStream(callbackResult);           
        byte[] byteArray = Encoding.UTF8.GetBytes(requestData);
        postStream.Write(byteArray, 0, byteArray.Length);
        postStream.Close();
        webrequest.BeginGetResponse(new AsyncCallback(GetResponsetStreamCallback), webrequest);

    }

    private void GetResponsetStreamCallback(IAsyncResult callbackResult)
    {
        Debug.WriteLine("we are in the third method");

        try
        {
            HttpWebRequest request = (HttpWebRequest)callbackResult.AsyncState;
            HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(callbackResult);
            string responseString = "";
            Stream streamResponse = response.GetResponseStream();
            StreamReader reader = new StreamReader(streamResponse);
            responseString = reader.ReadToEnd();
            streamResponse.Close();
            reader.Close();
            response.Close();
            requestResponse = responseString;

        }
        catch (Exception e)
        {
            //show user-friendly error message as well as detailed one.
            //for better UI, consider using WPToolKit's CustomMessageBox to show these
            Debug.WriteLine("something wrong happened. \nDetails: " + e.HResult.ToString());
        }
        Debug.WriteLine("we are about to return to initialize_request");
        objAuto.Set();
    } 

}
}