Linq to objects List in list

Question

I have a list of movies

List<Movie> MovieList

and I have a list of selected categories

List<string> SelCat

And say I want to select from the movie list where it matches 2 categories, like the SQL statement below:

SELECT * FROM MovieList WHERE MovieList.Category = 'Action' AND MovieList.Category = 'Drama'

I can get kinda close with linq like so:

var q = (from b in MovieList where b.Categories.Any(p=> SelCat.Contains(p)) select b);

But it acts like an OR query, not an AND. I want it to select all movies that have a category of action and drama.

BTW: Movie.Categories is a List of string. AND Movie.Categories must contain items in the SelCat.

How do I achieve this with Linq to Objects?

MovieList.Category = 'Action' AND MovieList.Category = 'Drama', don't you mean MovieList.Category = 'Action' OR MovieList.Category = 'Drama' — hazimdikenli
– hazimdikenli, Commented Nov 30, 2010 at 8:20
You want to find all films that are ACTION and DRAMA? So a film that only has DRAMA in its categories is not one you want? — Matt Ellen
– Matt Ellen, Commented Nov 30, 2010 at 8:27
Yes. All films that have action AND drama. or whatever is in the SelCat list of string. — Rick Rat
– Rick Rat, Commented Nov 30, 2010 at 8:28

Cheng Chen · Accepted Answer · 2010-11-30 08:39:05Z

8

var q = from m in MovieList where SelCat.All(c => m.Categories.Contains(c))

Quite close to what you would say describing the problem in English:

Select movies where the movie categories contain all the categories in SelCat.

edited Nov 30, 2010 at 8:39

Cheng Chen

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answered Nov 30, 2010 at 8:28

Jon

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Comments

hazimdikenli · Accepted Answer · 2010-11-30 08:31:33Z

1

   var SelectedCategories = List<string>();//list of selected categories

from movie in MovieList
join selCat in Categories.Where(SelectedCategories.Contains(selCat.Category)
on movie.category equals selCat.category
select movie

answered Nov 30, 2010 at 8:31

hazimdikenli

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Comments

Ani · Accepted Answer · 2010-11-30 08:39:49Z

1

If you want the movie to match all of the interesting categories (i.e. all of the categories in SelCat are present in movie.Categories), you can do:

MovieList.Where(movie => !SelCat.Except(movie.Categories).Any());

On the other hand, if you want the movie to match atleast 2 of the selected categories:

MovieList.Where(movie => SelCat.Intersect(movie.Categories).Count() >= 2);

edited Nov 30, 2010 at 8:39

answered Nov 30, 2010 at 8:29

Ani

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5 Comments

Rick Rat Over a year ago

Close, but I only get 132 records when I should have 183. Thanks for trying!

Cheng Chen Over a year ago

+1 the OP is giving a bad example. "Action" and "Drama" made others hard code, but essentially they are elements in the SelCat.

Ani Over a year ago

@Rick Ratayczak: If you can describe why this isn't what you want, that would be helpful.

Rick Rat Over a year ago

SelCat contains any number of strings in a List<string>. Movie.Categories must contain all of the SelCat items. Thank you anyways.

Ani Over a year ago

@Rick Ratayczak: That's exactly what my first query does.

user57508 · Accepted Answer · 2010-11-30 08:29:30Z

0

var result = from movie in movieList
             where selCat.All(selectedCategory => movie.Categories.Contains(selectedCategory))
             select movie;

remember the difference between .All() and .Any()

answered Nov 30, 2010 at 8:29

user57508

2 Comments

Jon Over a year ago

This will select movies whose categories are a subset of the selected categories. The OP wants to achieve the opposite effect.

Rick Rat Over a year ago

Thank you, but I get 0 records from that query.

digEmAll · Accepted Answer · 2010-11-30 08:29:44Z

0

A bit convoluted:

var moviesInSelCat = MovieList.Where(m => SelCat.All(sc => m.Category.Any(c => c == sc)));

edited Nov 30, 2010 at 8:29

answered Nov 30, 2010 at 8:24

digEmAll

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Comments

Dean Chalk · Accepted Answer · 2010-11-30 08:30:16Z

0

try this

var matches = MovieList.Where(m => SelCat.Except(
    m.Categories.Intersect(SelCat)).Count() == 0);

answered Nov 30, 2010 at 8:30

Dean Chalk

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1 Comment

Rick Rat Over a year ago

This is close also, but only returns 132 records when I know there is 183. Thank you!

Ali Tarhini · Accepted Answer · 2010-11-30 08:33:02Z

0

just do an intersect followed by except. it works, im sorry i had to write it in vb.

Dim categories As New List(Of String)
Dim selected As New List(Of String)

        categories.Add("ali")
        categories.Add("ali2")
        categories.Add("ali3")
        categories.Add("ali4")

        selected.Add("ali2")
        selected.Add("ali4")


        Dim common = categories.Intersect(selected)

        If common.Except(selected).Count = 0 Then
            'true
        Else
            'false
        End If

edited Nov 30, 2010 at 8:33

answered Nov 30, 2010 at 8:23

Ali Tarhini

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1 Comment

Rick Rat Over a year ago

Unfortunately, not the right answer. I don't know if it will be action or drama or comedy, but the Movie.Categories must contain items in the SelCat.

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