获取用户的主要组名称

通过属性memberof可以获取用户的所有组，但除了主要组.

不过可以通过primaryGroupID来获取，虽然它返回的是rid

尝试用rid作为filter，但总是取不回结果来。

最后只好通过objectSid，但objectSid是个byte[]类型，所以通过filter也获取不到，最后只好通过把所有的组缓存到本地，然后来获取组名称，代码如下：

public string[] GetAllGroupsForUser(string username)
        {
            
            var searcher = new DirectorySearcher(Utility.GetDomainDirectoryEntry());
            searcher.Filter = "(&(sAMAccountName=" + trueUserName.Trim() + "))";
            searcher.PropertiesToLoad.Add("memberof");
            searcher.PropertiesToLoad.Add("primaryGroupID");

            SearchResultCollection searchCollecton = searcher.FindAll();
            var groups = new List<string>();

            foreach (SearchResult searchResult in searchCollecton)
            {
                if (searchResult.Properties["memberof"] == null)
                {
                    return (null);
                }

                foreach (var memberof in searchResult.Properties["memberof"])
                {
                    groups.Add(memberof.ToString().Substring(3, memberof.ToString().IndexOf(",") - 3));
                }

                if (searchResult.Properties["primaryGroupID"].Count > 0)
                {
                    groups.Add(GetGroupNameByRid((Int32)searchResult.Properties["primaryGroupID"][0]));
                }
            }

            return groups.ToArray();
        }

        public String GetGroupNameByRid(Int32 rid)
        {
            String result;
            if (groupNames.TryGetValue(rid, out result)) return result;
            else ReloadGroupNames();

            return groupNames[rid];
        }

        private void ReloadGroupNames()
        {
            lock (loadGroupLock)
            {
                var searcher = new DirectorySearcher(Utility.GetDomainDirectoryEntry());
                searcher.Filter = "(&(objectClass=group))";  //获取所有的组
                searcher.PropertiesToLoad.Add("objectSid"); //获取组的objectSid
                searcher.PropertiesToLoad.Add("name");  //获取组的名称

                SearchResultCollection searchResults = searcher.FindAll();

                foreach (SearchResult searchResult in searchResults)
                {
                    //从sid中获取rid
                    SecurityIdentifier secId = new SecurityIdentifier(searchResult.Properties["objectSid"][0] as byte[], 0);
                    Regex regRID = new Regex(@"^S.*-(\d+){1}quot;);
                    Match matchRID = regRID.Match(secId.Value);
                    string sRID = matchRID.Groups[1].Value;

                    Int32 rid = Int32.Parse(sRID); 
                    if (groupNames.ContainsKey(rid)) continue;
                    groupNames.Add(rid,(String)searchResult.Properties["name"][0]);
                }
            }
        }

        private static Object loadGroupLock = new object(); //锁 
        private static Dictionary<Int32, String> groupNames = new Dictionary<int, string>(); //保存rid和name