public CategoryVM(User _user)
{
Title = "Категории";
User = _user;
Categories = new ObservableCollection <Category>();
repository = new CategoryRepository(User);
LoadItemsCommand = new Command(async() => await ExecuteLoadItemsCommand());
MessagingCenter.Subscribe <NewCategoryPage, Category>(this, "AddCategory", async(obj, item) =>
{
var newItem = item as Category;
Categories.Add(newItem);
await repository.AddItemAsync(newItem);
});
}