How to share cookies between domain.com and www.domain.com?

Question

I'm using HttpWebRequest to download data from the website, and I noticed a bug related to the cookies. When you get the data from domain.com, and that website redirects to www.domain.com, which sends a cookie, that cookie isn't shared with domain.com. This causes some nasty bugs in my app.

I know that www.domain.com is not necessary the same website as domain.com, but I believe that in this case the benefits will outweigh any associated risks.

Is there any easy way to automatically apply cookies from domain.com to www.domain.com and vice verse?

Answer 1

Here's what I did:

    class DomainComparer : StringComparer
    {
        public override int Compare(string x, string y)
        {
            if (x == null || y == null)
            {
                return StringComparer.OrdinalIgnoreCase.Compare(x, y);
            }
            if (x.StartsWith("www.", StringComparison.OrdinalIgnoreCase))
            {
                x = x.Substring(4);
            }
            if (y.StartsWith("www.", StringComparison.OrdinalIgnoreCase))
            {
                y = y.Substring(4);
            }
            return StringComparer.OrdinalIgnoreCase.Compare(x, y);
        }

        public override bool Equals(string x, string y)
        {
            return Compare(x, y) == 0;
        }

        public override int GetHashCode(string obj)
        {
            if (obj.StartsWith("www.", StringComparison.OrdinalIgnoreCase))
            {
                obj = obj.Substring(4);
            }
            return StringComparer.OrdinalIgnoreCase.GetHashCode(obj);
        }
    }

    /// <summary>
    /// this is a hackfix for microsoft bug, where cookies are not shared between www.domain.com and domain.com
    /// </summary>
    /// <param name="cc"></param>
    static void ImproveCookieContainer(CookieContainer cc)
    {
        Hashtable table = (Hashtable)cc.GetType().InvokeMember(
            "m_domainTable",
            System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.GetField | System.Reflection.BindingFlags.Instance,
            null, cc, new object[] { });
        var comparerPreperty = table.GetType().GetField("_keycomparer", 
            System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.GetField | System.Reflection.BindingFlags.Instance);
        if (comparerPreperty != null)
        {
            comparerPreperty.SetValue(table, new DomainComparer());
        }
    }

Answer 2

Store your cookie content in a session object and call the new page with a session key identifying your session object. Then lookup the session and set a new cookie when delivering the page for www.domain.com.