How to get all the AD groups for a particular user?

I checked this post already. But it doesn't answer my question. I want to get all the active directory groups in which a particular user is a member.

I've written the following code. But I'm not able to proceed further as I don't know how to give the filter and how to access the properties.

class Program
{
    static void Main(string[] args)
    {
        DirectoryEntry de = new DirectoryEntry("LDAP://mydomain.com");
        DirectorySearcher searcher = new DirectorySearcher(de);
        searcher.Filter = "(&(ObjectClass=group))";
        searcher.PropertiesToLoad.Add("distinguishedName");
        searcher.PropertiesToLoad.Add("sAMAccountName");
        searcher.PropertiesToLoad.Add("name");
        searcher.PropertiesToLoad.Add("objectSid");
        SearchResultCollection results = searcher.FindAll();
        int i = 1;
        foreach (SearchResult res in results)
        {
            Console.WriteLine("Result" + Convert.ToString(i++));
            DisplayProperties("distinguishedName", res);
            DisplayProperties("sAMAccouontName", res);
            DisplayProperties("name", res);
            DisplayProperties("objectSid", res);
            Console.WriteLine();
        }

        Console.ReadKey();
    }

    private static void DisplayProperties(string property, SearchResult res)
    {
        Console.WriteLine("\t" + property);
        ResultPropertyValueCollection col = res.Properties[property];
        foreach (object o in col)
        {
            Console.WriteLine("\t\t" + o.ToString());
        }
    }
}

Any ideas?