LINQ: Select where object does not contain items from list

Question

I'm struggling with LINQ syntax here...thought I'd toss it out here. I cant find exactly what I'm looking for anywhere else.

OK, say I've got this:

public class Bar
{
   public int BarId { get; set; }
}

public class Foo
{
   public List<Bar> BarList { get; set; }
}

List<Foo> fooBunch = GetABunchOfFoos(); //let's just assume I'm getting more than one
List<Foo> fooSelect = new List<Foo>;
List<Bar> filterBars = GetAFewBars(); //assume I'm getting like 2 or 3

fooSelect = (from f in fooBunch
             where !(from b in f.BarList select b.BarId).Contains(ITEM FROM filterBars.BarId)
             select f).ToList();

So, long story short I want to use LINQ to filter out my list of objects based on objects from another list. I hope this makes sense. I think I'm just lost on the Contains portion...I don't know how to write that.

Thebigcheeze · Accepted Answer · 2011-04-12 19:39:21Z

141

In general, you're looking for the "Except" extension.

var rejectStatus = GenerateRejectStatuses();
var fullList = GenerateFullList();
var rejectList = fullList.Where(i => rejectStatus.Contains(i.Status));
var filteredList = fullList.Except(rejectList);

In this example, GenerateRegectStatuses() should be the list of statuses you wish to reject (or in more concrete terms based on your example, a List<int> of IDs)

edited Apr 12, 2011 at 19:39

answered Apr 12, 2011 at 19:09

Thebigcheeze

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3 Comments

farina Over a year ago

This is really close...the trick would be to create the rejectList from dynamic statuses. It would be more like where i => i.Status in(list<statuses>). Can I do something like that? Basically another LINQ statement I guess?

Thebigcheeze Over a year ago

Absolutely, to build the rejectList, you'd just have to devise a way to get a list of rejects you don't want. For example: var rejectList = fullList.Where(i => rejectStatuses.Contains(i.Status)); I'll update my original answer to reflect this change.

JustJohn Over a year ago

How would I do this in just one line? I understand it might not be possible.

hunter · Accepted Answer · 2011-04-12 19:09:30Z

96

dump this into a more specific collection of just the ids you don't want

var notTheseBarIds = filterBars.Select(fb => fb.BarId);

then try this:

fooSelect = (from f in fooBunch
             where !notTheseBarIds.Contains(f.BarId)
             select f).ToList();

or this:

fooSelect = fooBunch.Where(f => !notTheseBarIds.Contains(f.BarId)).ToList();

answered Apr 12, 2011 at 19:09

hunter

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5 Comments

JoshYates1980 Over a year ago

Nice. i like this answer better. +1

Rarepuppers Over a year ago

This answer is better than the selected

Cata Hotea Over a year ago

Clean and simple ! Nice

jleach Over a year ago

@Rarepuppers - I spend a few minutes trying to understand the accepted answer, then looked here to see suggested what I already typed before I knew for sure if it worked that way...

Xonshiz Over a year ago

This should be the accepted answer. I've been looking to UNDERSTAND how it works. Thanks a ton!

Thomas Smyth · Accepted Answer · 2018-01-10 16:16:13Z

7

Try this simple LINQ:

//For a file list/array
var files = Directory.GetFiles(folderPath, "*.*", SearchOption.AllDirectories);

//simply use Where ! x.Contains
var notContain = files.Where(x => ! x.Contains(@"\$RECYCLE.BIN\")).ToList();

//Or use Except()
var containing = files.Where(x => x.Contains(@"\$RECYCLE.BIN\")).ToList();
    notContain = files.Except(containing).ToList();

edited Jan 10, 2018 at 16:16

Thomas Smyth

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answered Jan 10, 2018 at 16:08

alex

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Comments

sehe · Accepted Answer · 2013-10-29 14:41:23Z

5

I have not tried this, so I am not guarantueeing anything, however

foreach Bar f in filterBars
{
     search(f)
}
Foo search(Bar b)
{
    fooSelect = (from f in fooBunch
                 where !(from b in f.BarList select b.BarId).Contains(b.ID)
                 select f).ToList();

    return fooSelect;
}

edited Oct 29, 2013 at 14:41

sehe

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answered Apr 12, 2011 at 19:10

Tony The Lion

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2 Comments

farina Over a year ago

From what I can tell, b.ID doesn't compile. The Contains method seems to loose context of b.

Justin Morgan Over a year ago

You're using two variables named b, and the compiler probably finds it ambiguous.

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