private bool GetChecked(ItemVM item)
        {
            var key = item.Ref;

            if (UserData != null && UserData.ReadItems.ContainsKey(key))
            {
                return(UserData.ReadItems[key].Checked);
            }
            return(false);
        }
        private void ItemVMCheckedChanged(ItemVM item, bool chked)
        {
            if (UserData == null)
            {
                UserData = new LeseplanUserData();
            }
            var key = item.Ref;

            if (!UserData.ReadItems.ContainsKey(key))
            {
                UserData.ReadItems[key] = new ItemReadData {
                    Ref = item.Ref
                };
            }
            UserData.ReadItems[key].Checked = chked;
            SaveUserData();
        }