How would you suggest to in C# all users in GrpA and Grp B stored them in GrpAB using List<string>
 <p>   This is my current solution. Any better search algorithms?</p>

<pre>   public void membersOfBothGroup(string groupA,string groupB)
        {
            List usersInGroupA = getGroupMembers(groupA);
            List usersInGroupB = getGroupMembers(groupB);
            List userInBothAB = new List();
            foreach (string userA in usersInGroupA)
            { 
                foreach(string userB in usersInGroupB)
                {
                    if (userA == userB)
                    {
                        userInBothAB.Add(userA);
                    }
                }
            }
        }
</pre>
