Linq select where in list

Question

I have the following class

public class Group
{
    public string Id { get; set; }
    public string Name { get; set; }
}

and 2 lists List<string> groupRestrict and List<Group> groups

now the group list contains some groups with all fields filled in and I want to select all the restricted groups, the groupRestrict list contains just the name of the groups.

I tried some things, but for some reasons, it always returns an empty list. this as my last test:

var lst = groups.Where(j => groupRestrict.Contains(j.Name)).ToList();

Any clue what might be going wrong?

Edit: Like the comments said, this should have worked, it was the input that had some ' but now I would like to have that the groupRestrict doesn't have to be the exact name, but can use 'like' features.

current expression:

var restrictedGroups = (from gr in groupRestrict join g in groups on gr equals g.Name select g).ToList();

Be aware that this is a bigO - rather do this query on a HashSet (or Dictionary) and think about using .Join or .GroupJoin (whether you want a left or full join) — user57508
– user57508, Commented Feb 23, 2015 at 13:01
@AndreasNiedermair it's not on a SQL database, if that is what you are refering to :) — Kiwi
– Kiwi, Commented Feb 23, 2015 at 13:02
This should work. Be aware that string comparison is case sensitive by default. — helb
– helb, Commented Feb 23, 2015 at 13:03
Sounds like it should work (albeit relatively inefficiently if groupRestrict is large) - please show a short but complete program demonstrating the problem. — Jon Skeet
– Jon Skeet, Commented Feb 23, 2015 at 13:04

Florian Schmidinger · Accepted Answer · 2015-02-23 14:29:39Z

2

Try:

var lst = groups.Where(j => groupRestrict.Any(x=> j.Name.Contains(x))).ToList();

this would match all groups with names that contain one or more strings from the searchList.

Case insensitive variant would be:

var lst = groups.Where(j => groupRestrict.Any(x=> j.Name.ToLower().Contains(x.ToLower()))).ToList();

Allthough it would be better to convert the groupRestrict to lowercase prior to the query in this case and you can omit the .ToLower() call for x:

string[] lowerCaseGroupRestrict = groupRestrict.Select(x=> x.ToLower()).ToArray();
var lst = groups.Where(j => lowerCaseGroupRestrict.Any(x=> j.Name.ToLower().Contains(x))).ToList();

edited Feb 23, 2015 at 14:29

answered Feb 23, 2015 at 13:47

Florian Schmidinger

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2 Comments

Kiwi Over a year ago

Nice thanks! The groupRestrict is a user input (although it's get checked and filtered first) . so the prior can be easy called :)

Kiwi Over a year ago

Sorry, totally forgot it! :)

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