C#异步调用后如何看到状态码？
C#异步调用的代码如下：

public class DataRequest
{
    public string paramData=string.Empty;//请求参数
    public string resData=string.Empty;//返回值
    public HttpStatusCode statusCode;//状态记录
    public Exception errorAsync;//记录异步函数中的错误
    public static Encoding dataEncode = Encoding.UTF8;//字符编码方式为UTF8
    public void RequestURL(string url)
    {
        HttpWebRequest webReq = (HttpWebRequest)WebRequest.Create(new Uri(url));
        webReq.Method = "POST";
        webReq.ContentType = "application/x-www-form-urlencoded";
        webReq.BeginGetRequestStream(new AsyncCallback(GetRequestStreamCallback), webReq);
    }
    private void GetRequestStreamCallback(IAsyncResult asynchronousResult)
    {
        try
        {
            HttpWebRequest request = (HttpWebRequest)asynchronousResult.AsyncState;
            Stream postStream = request.EndGetRequestStream(asynchronousResult);
            byte[] byteArray = dataEncode.GetBytes(paramData);
            postStream.Write(byteArray, 0, byteArray.Length);
            postStream.Close();
            request.BeginGetResponse(new AsyncCallback(GetResponseCallback), request);
        }
        catch (Exception ee)
        {
            errorAsync = ee;
         }
    }
    private void GetResponseCallback(IAsyncResult asynchronousResult)
    {
        try
        {
            HttpWebRequest request = (HttpWebRequest)asynchronousResult.AsyncState;
            HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(asynchronousResult);
            Stream streamResponse = response.GetResponseStream();
            StreamReader streamRead = new StreamReader(streamResponse);
            statusCode=response.StatusCode;
            resData = streamRead.ReadToEnd();
            streamResponse.Close();
            streamRead.Close();
        } 
 
        catch (Exception ee) 
        {
             errorAsync = ee;
        }
    }
}

可是通过MessageBox.Show()看到的状态码却为0，也就是状态码是空值，代码如下：

DataRequest request = new DataRequest();
username = System.Net.HttpUtility.UrlEncode(username);
password = MD5CryptoServiceProvider.GetMd5String(password);
request.paramData = @"EMAIL=" + username + @"&PASSWORD=" + password + @"&debug=";
request.RequestURL(baseUrl + "login.php");
MessageBox.Show(request.statusCode.ToString());

这是什么原因？我该如何看到状态码？
[解决办法]
原来那个回调函数没有开启新的线程,仍然是由UI的线程来负责处理的.HttpWebRequest是基于后台进程运行的，回调不是UI线程，所以不能直接对UI进行操作，通常使用Dispatcher.BeginInvoke()跟界面进行通讯。Notify的 Signal是全局信号量，是线程安全的.API的请求使用异步的，得到数据后存起来，然后发信号给等待的UI线程.基本是这么个思路