Question

我目前正在开发一个类，帮助我使用cookie和POST参数创建WebRequest。但response.cookies总是空的。如何获取返回的cookie并在下次请求时发送它们？

class WebHandler
{
    private string lasturl = "";
    private Dictionary<string, Cookie> cookies;
    public string lastContent;

    public WebHandler()
    {
        cookies = new Dictionary<string, Cookie>();
    }

    public HttpWebResponse request(string address)
    {
        lasturl = address;
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(address);
        foreach (KeyValuePair<string, Cookie> pair in this.cookies)
        {
            Console.WriteLine(" Sent cookie: " + pair.Value.Name + " = " + pair.Value.Value);
            request.CookieContainer.Add(pair.Value);
        }
        request.Method = "GET";
        if(lasturl != "")
            request.Referer = lasturl;

        HttpWebResponse response = (HttpWebResponse)request.GetResponse();
        foreach (Cookie newCookie in response.Cookies)
        {
            Console.WriteLine(" new cookie: " + newCookie.Name + " = " + newCookie.Value);
            this.cookies[newCookie.Name] = newCookie;
        }
        lastContent = new StreamReader(response.GetResponseStream()).ReadToEnd();
        return response;
    }

    public HttpWebResponse request(string address, Dictionary<string, string> postParameters)
    {
        lasturl = address;
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(address);
        foreach (KeyValuePair<string, Cookie> pair in this.cookies)
        {
            Console.WriteLine(" Sent cookie: " + pair.Value.Name + " = " + pair.Value.Value);
            request.CookieContainer.Add(pair.Value);
        }
        request.Method = "POST";

        string postData = "";
        foreach (string key in postParameters.Keys)
            postData += HttpUtility.UrlEncode(key) + "=" + HttpUtility.UrlEncode(postParameters[key]) + "&";


        byte[] data = Encoding.ASCII.GetBytes(postData);
        request.ContentType = "application/x-www-form-urlencoded";
        request.ContentLength = data.Length;
        Stream requestStream = request.GetRequestStream();
        requestStream.Write(data, 0, data.Length);
        requestStream.Close();

        HttpWebResponse response = (HttpWebResponse)request.GetResponse();
        foreach (Cookie newCookie in response.Cookies)
        {
            Console.WriteLine(" new cookie: " + newCookie.Name + " = " + newCookie.Value);
            this.cookies[newCookie.Name] = newCookie;
        }
        lastContent = new StreamReader(response.GetResponseStream()).ReadToEnd();
        return response;
    }
}

Answer 1

由于this.cookies最初为null，因此您的代码永远不会进入循环

foreach (KeyValuePair<string, Cookie> pair in this.cookies)
{
     Console.WriteLine(" Sent cookie: " + pair.Value.Name + " = " + pair.Value.Value);
     request.CookieContainer.Add(pair.Value);
}

你从未见过request.CookieContainer的坏部分是空的（否则你会得到 null引用异常），这会显示出错了。

由于request.CookieContainer为空，HttpWebResponse永远不会获得返回的cookie。

解决方案：简单，只需添加

if (request.CookieContainer == null) 
         request.CookieContainer = new CookieContainer();

后

HttpWebRequest request = (HttpWebRequest)WebRequest.Create(address);

PS：您可能希望阅读有关c＃中命名约定的this question。

PS2：使用变量名request的方法request不会提高可读性。

Answer 2

我遇到了同样的问题，所以我添加了request.AllowAutoRedirect=false;，现在我可以获得Cookie：

HttpWebRequest request = (HttpWebRequest)WebRequest.Create(address);
...
request.Method = "POST";
request.AllowAutoRedirect=false;

Answer 3

如果HttpWebResponse对象的Cookies集合为空，则表示响应没有新的Cookie。要访问所有Cookie以获取请求和响应，请从HttpWebRequest对象中读取Cookie，如下所示：

foreach (Cookie newCookie in request.Cookies)
{
    // Do something with cookies here for next request
}

WebResponse不会返回任何cookie

3 个答案: