C#

public class GroupPrincipalExt : GroupPrincipal
    {
        public GroupPrincipalExt(PrincipalContext context) : base(context) { }
        public GroupPrincipalExt(PrincipalContext context, string groupName) : base(context, groupName) { }

        public static new GroupPrincipalExt FindByIdentity(PrincipalContext context, string identityValue)
        {
            return (GroupPrincipalExt)FindByIdentityWithType(context, typeof(GroupPrincipalExt), identityValue);
        }

        public static new GroupPrincipalExt FindByIdentity(PrincipalContext context, IdentityType identityType, string identityValue)
        {
            return (GroupPrincipalExt)FindByIdentityWithType(context, typeof(GroupPrincipalExt), identityType, identityValue);
        }

        [DirectoryProperty("wWWHomePage")]
        public string WWWHomePage
        {
            get
            {
                if (ExtensionGet("wWWHomePage").Length != 1)
                    return null;

                return (string)ExtensionGet("wWWHomePage")[0];
            }
            set
            {
                this.ExtensionSet("wWWHomePage", value);
            }
        }
}

using (PrincipalContext pc = new PrincipalContext(ContextType.Domain, "dc.******.local", "DC=*****,DC=local", ContextOptions.SimpleBind, "******\\Administrator", "*********"))
                {

                    GroupPrincipalExt group = GroupPrincipalExt.FindByIdentity(pc, IdentityType.DistinguishedName, distinguishedname);
                    if (group != null)
                    {
}
}