1 public List<GroupPrincipal> GetGroups(string userName)
 2 {
 3    List<GroupPrincipal> result = new List<GroupPrincipal>();
 4 
 5    // establish domain context
 6    PrincipalContext yourDomain = new PrincipalContext(ContextType.Domain);
 7 
 8    // find your user
 9    UserPrincipal user = UserPrincipal.FindByIdentity(yourDomain, userName);
10 
11    // if found - grab its groups
12    if(user != null)
13    {
14       PrincipalSearchResult<Principal> groups = user.GetAuthorizationGroups();
15 
16       // iterate over all groups
17       foreach(Principal p in groups)
18       {
19          // make sure to add only group principals
20          if(p is GroupPrincipal)
21          {
22              result.Add((GroupPrincipal)p);
23          }
24       }
25    }
26 
27    return result;
28 }