如何过滤C＃中另一个列表的一部分的子列表

Question

I want to filter the list which is already part of another list.

Consider,

Class MainClass

  properties

      String Name

      String MainAddress

      List<SubClass> ExtraInfo

Class SubClass

  properties

      String Address

      String City

      String PhoneNo

Now i have 10 items in my List and each item in List has 2 ExtraInfo items this is List items.

Now i want to filter List items with Condition City == "New York".

So, all 10 items in the main list (List) should have the ExtraInfo (List) items based on the filter condition.

I mean i just want to filter the Sub list not the main list.

Thanks in Advance!

Sample Data Name MainAddress ExtraInfo Address City Phone No
1. Vimal Bangalore North Street New York 654564646 --->Sub item 1 North Street California 464654565 --->Sub item 2

1. Hareesh Chennai North Street Washington 546466466 --->Sub item 1 Tower B New York 464645465 --->Sub item 2

After Filter (Condition City == "New York"), I should get the output in the main list like

 Name      MainAddress       ExtraInfo
                                Address        City        Phone No      

1. Vimal Bangalore North Street New York 654564646 --->Sub item 1

1. Hareesh Chennai Tower B New York 464645465 --->Sub item 1

Hope this helps!

Answer 1

I might not have understood the question correctly, but:

List<MainClass> mainList = ...
mainList.ForEach(m => m.ExtraInfo.RemoveAll(subClass => subClass.City != "New York"));

This will modify each item in mainList in place, by removing all items from its list-member ExtraInfo (in place) for which each item in the list (of type SubClass ) does not have "New York" as its City . Is that what you want?

If you simply want all of the 'embedded' ExtraInfo items that match the filter no matter which MainClass's list they belong to, you could do this:

var filteredSubClasses = mainList.SelectMany(m => m.ExtraInfo)
                                 .Where(subClass => subClass.City == "New York");

EDIT: Based on the OP's comment: This is a bit ugly, but should be what you need:

var filteredList = mainList.Select(m => new MainClass
                            { 
                               Name = m.Name;
                               MainAddress = m.MainAddress;
                               ExtraInfo = m.ExtraInfo
                                            .Where(subClass => subClass.City == "New York")
                                            .ToList()
                            })
                          .ToList();

IMO, it would be easier if MainClass supplied a copy-constructor or clone-method to remove the need to copy all the properties over one by one. This is a bit brittle - it will break if you add a new property to MainClass .

Answer 2

You have to filter each of the sublists:

List<MainClass> mainList = ...
foreach(MainClass main in mainList)
{
    ICollectionView view = CollectionViewSource.GetDefaultView(main.ExtraInfo);
    view.Filter = ExtraInfoFilter;
}

bool ExtraInfoFilter(object obj)
{
    ExtraInfo item = (ExtraInfo)obj;

    return item.City == "New York";
}