在异步 Web 请求失败中设置请求属性。 C#

Question

private void LoginButton_Click(object sender, EventArgs e)
{
    try
    {
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(loginUrl);
        IAsyncResult result = request.BeginGetResponse(
            new AsyncCallback(DeleResponse), request);
    }
    catch(Exception ex)
    {
        MessageBox.Show(ex.Message);
    }
}

这是调用按钮单击事件的方法

private void DeleResponse(IAsyncResult result)
{
    byte[] PostData = Encoding.UTF8.GetBytes("username=" + userInp.Text + "&password=" + passInp.Text + extraLoginPostString);
    LoginButton.Text = "Logging in...";
    LoginButton.Enabled = false;
    HttpWebRequest request = (HttpWebRequest)result.AsyncState;
    request.Method = "Post";
    request.CookieContainer = authCookie;
    request.ContentType = "application/x-www-form-urlencoded";
    request.AllowAutoRedirect = false;
    postWriter = request.GetRequestStream();
    postWriter.Write(PostData, 0, PostData.Length);
    postWriter.Close();
        HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(result);
        string serverData = new StreamReader(response.GetResponseStream()).ReadToEnd();
    string loginValidateString = response.GetResponseHeader(loginValidateStringHolder);
    if (loginValidateString.Contains(LoggedKeyword))
    { 
            some process here:
        }
        else if( FAILKEYWORDCHECK HERE)
        {
            login page process here;
        }
    }

问题是当我用 fiddler 检查它时我只能看到以下标头属性。

Connection: Keep-Alive;
Host: www.example.com

我无法在请求标头中设置属性的原因是什么？

编辑：添加了我已经实现的同步请求方法，没有任何错误。

 private void LoginButton_Click(object sender, EventArgs e)
    {
        try
        {
           LoginButton.Text = "Logging in...";
            LoginButton.Enabled = false;
            byte[] PostData = Encoding.UTF8.GetBytes("username=" + userInp.Text + "&password=" + passInp.Text + extraLoginPostString);
            request = (HttpWebRequest)WebRequest.Create(loginUrl);
            request.Method = "Post";
            request.CookieContainer = authCookie;
            request.ContentType = "application/x-www-form-urlencoded";
            request.AllowAutoRedirect = false;

            postWriter = request.GetRequestStream();
            postWriter.Write(PostData, 0, PostData.Length);
            postWriter.Close();

            response = (HttpWebResponse)request.GetResponse();

            string serverData = new StreamReader(response.GetResponseStream()).ReadToEnd();
            string loginValidateString = response.GetResponseHeader(loginValidateStringHolder);
            if (loginValidateString.Contains(LoggedKeyword))
            {
                MessageBox.Show("Logged in Successfully");

                foreach (Cookie cookieReader in response.Cookies)
                {
                    authCookie.Add(cookieReader);
                }
                Success method continues..
            }
            else if (loginValidateString.Contains(failedLogKeyword))
            {
                Failed process
            }
        }
        catch
        {
            Catchblock
        }
        }

意味着，我只知道如何为正常请求设置属性。

Answer 1

当响应可用时，您尝试设置请求的属性。您需要在向服务器发出请求之前设置请求属性 - 因此您应该在 LoginButton_Click 中设置它们，而不是在响应处理代码中设置它们。同样，您不能在 BeginGetResponse 的回调中使用 GetRequestStream。粗略地说，您想要：

• 在初始事件处理程序中：
  • 创建请求
  • 设置简单属性
  • 调用BeginGetRequestStream
• 在 BeginGetRequestStream 的回调处理程序中
  • 写出正文数据
  • 调用BeginGetResponse
• 在 BeginGetResponse 的回调处理程序中
  • 处理响应数据

或者，除非您必须使用异步调用，否则您可以创建一个单独的线程并使用同步版本。在 C# 5 提供语言支持之前，这会更简单。