AD Domain 认证查询

传出员工号等信息，查询此人是否在AD中存在：

 public bool ValidateEmpNoAndEmailId(string vEmpNo, string vEmailId)
        {
            DirectoryEntry rootEntry = new DirectoryEntry("LDAP://ad.home.com");
            DirectorySearcher srch = new DirectorySearcher(rootEntry);
            srch.SearchScope = SearchScope.Subtree;

           //搜寻条件....

　　　　srch.Filter = "(&(objectcategory=user)(sAMAccountName=" + vEmailId + "))";
            SearchResultCollection res = srch.FindAll();
            bool flag = res.Count <= 0 ? false : true;

            srch.Filter = "(&(objectcategory=user)(company=" + vEmpNo + "))";
            res = srch.FindAll();
            flag = (flag == false) && res.Count <= 0 ? false : true;

            return flag;
        }