WebResponse不返回任何cookie

Question

我目前正在研究可幫助我使用Cookie和POST參數創建WebRequest的類。 但是response.cookies始終為空。 如何獲取返回的Cookie並在下一個請求中發送它們？

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

由於this.cookies最初為null，因此您的代碼永遠不會進入循環

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

它的request.CookieContainer是您永遠不會看到request.CookieContainer為null（否則您將獲得null引用異常 ），這表明您有問題。

由於request.CookieContainer為null，因此HttpWebResponse永遠不會獲取返回的cookie。

解決方案：簡單，只需添加

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

后

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

---

PS：您可能想閱讀有關c＃中的命名約定的問題 。

PS2：在方法request使用一個變量名request不提高可讀性。

Answer 2

我有同樣的問題，所以我添加了request.AllowAutoRedirect=false; ，現在我可以獲取Cookie了：

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

Answer 3

如果HttpWebResponse對象的Cookies集合為空，則意味着響應中沒有新的Cookies。 要訪問所有cookie以進行請求和響應，請改為從HttpWebRequest對象讀取cookie，如下所示：

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