c# - 您知道执行此 "massive"linq 过滤的另一种方法吗？

Question

这是我的代码:

// I STORE THE USER SELECTED VALUES
IList<string> SelectedCity = (from CheckBox loc in panelCity.Controls.OfType<CheckBox>()
                              where loc.Checked
                              select loc.InputAttributes["value"]).ToList();

IList<string> SelectedCategories = (from CheckBox strut in panelCategories.Controls.OfType<CheckBox>()
                                    where strut.Checked
                                    select strut.InputAttributes["value"]).ToList();

// I GET ALL RECORDS
IList<Hotel> Hotels = (from Hotel hotel in new Hotels()
                       orderby hotel.Titolo ascending
                       select hotel).ToList();

// I FILTER THEM
if (SelectedCity.Count > 0)
    Hotels = Hotels.Where(o => o.City != null && SelectedCity.Contains(o.City.UniqueID)).ToList();

if (SelectedCategories.Count > 0)
    Hotels = Hotels.Where(o => o.Category != null && SelectedCategories.Contains(o.Category.UniqueID)).ToList();

因此，如您所见，我进行了一些查询，存储了从用户那里选择的值。然后，对于每一行酒店，我循环 City 和 Category 的数组。

这个，有很多行，非常昂贵。

您知道优化研究的其他一些方法吗？

Answer 1

将您的城市和类别放入 HashSet<string>节省查找时间:

HashSet<string> selectedCities = new HashSet<string>(SelectedCity); 
HashSet<string> selectedCategories = new HashSet<string>(SelectedCategories); 

你也不需要使用 ToList()直到您的查询完全组装好，否则您将遍历多次:

var hotels = from Hotel hotel in new Hotels()
             select hotel;

if (SelectedCity.Any())
    hotels = hotels.Where(o => o.City != null && selectedCities.Contains(o.City.UniqueID));

if (SelectedCategories.Any())
    hotels = hotels.Where(o => o.Category != null && selectedCategories.Contains(o.Category.UniqueID));

最后，一旦您过滤掉所有您不想要的酒店就可以进行排序，因此您排序的项目较少:

hotels = hotels.OrderBy(h=> h.Titolo);

作为最后一步，实现结果:

Hotels = hotels.ToList();