/// <summary>
/// Function try get data from db,
/// if request isn't the first, return data from cache
/// else do new request to db and return them
/// </summary>
/// <returns>Products list</returns>
public List <ProductDto> GetProducts()
{
_products = _databaseBase.GetDatabaseList <ProductDto>().Result;
if (_products.IsNullOrEmpty() || _products.Any(i => i.Article == 0))
{
throw new NullReferenceException();
}
return(_products);
}