private void Register()
        {
            string error = RegisterPageMemberModel.EnableValidationAndGetError();

            if (error != null)
            {
                return;
            }

            MemberModel tempMemberModel = new MemberModel();

            tempMemberModel.CopyFrom(RegisterPageMemberModel);

            MemberModels.members.Add(tempMemberModel);

            TreeCategory parent = TreeViewMaker.FindNewParent(TreeItemModel.TreeCategories, RegisterPageMemberModel.Age);

            if (parent != null)
            {
                parent.Children.Add(tempMemberModel);
            }

            RegisterPageMemberModel.Clear();
            MessageBoxService.MessageBoxServiceShow(registerCompletedMessage);
        }
        private void Delete(object selectedMenuItem)
        {
            MemberModel selectedMemberModel = selectedMenuItem as MemberModel;

            if (selectedMemberModel == null)
            {
                return;
            }

            MessageBoxResult result = MessageBoxService.MessageBoxServiceShow(deleteConfirmMessage, deleteConfirmCaption);

            if (result == MessageBoxResult.No)
            {
                return;
            }

            TreeCategory treeCategory = TreeViewMaker.FindNewParent(TreeItemModel.TreeCategories, selectedMemberModel.Age);

            treeCategory.Children.Remove(selectedMemberModel);
            MemberModels.members.Remove(selectedMemberModel);
            ListPageMemberModel.Clear();
        }