using System.DirectoryServices;
using System.Reflection;

 
public class ADGroup
{
 
   private String ADGRPOUP = "group";
 
   enum GrpType : uint
   {
      UnivGrp = 0x08,
      DomLocalGrp = 0x04,
      GlobalGrp = 0x02,
      SecurityGrp = 0x80000000
   }
 
   DirectoryEntry MyDirectoryEntry = new DirectoryEntry("LDAP://RootDSE");
   String Mystr = (String) MyDirectoryEntry.Properties["defaultNamingContext"][0];
   MydeAD = new DirectoryEntry("LDAP://" + Mystr);
   GrpType Mygt = GrpType.GlobalGrp | GrpType.SecurityGrp;
   int MytypeNum = (int)Mygt; 
   DirectoryEntry Myou = MydeAD.Children.Find("OU=Users");
   DirectoryEntry Mygroup = Myou.Children.Add("cn=myGroupName", ADGRPOUP );
   Mygroup.Properties["sAMAccountName"].Add("myGroupName");
   Mygroup.Properties["description"].Add(" description myGroupName");
   Mygroup.Properties["groupType"].Add(typeNum);
   Mygroup.CommitChanges();
}