What's the syntax for this linq expression calling the in method

Question

I have to query a repository where column a = {myvalue} and column b has any value in a collection.

Here's what I have:

Application[] applicationCollection = GetAllApplications();
var result = repo.GetAll(r => r.Email == myEmail && r.Application.In(applicationCollection));

I can't figure out how to write the "in" part...

Preferrably links to how to do this would be best, so I can learn it, as opposed to just getting the answer :). Thanks all.

(I'm sure this is a repeat question, but my Google/search skills are obviously poor.)

Are you saying that you know when `applicationCollection` *contains* `r.Application`? — Gabe, Jul 15 '13 at 22:40

score 1 · Accepted Answer · answered Jul 15 '13 at 22:40

1

The SQL idea of item in collection is written in C# (including LINQ) as collection.Contains(item). In your example, this might be:

var result = repo.GetAll(r => r.Email == myEmail &&
               applicationCollection.Contains(r.Application));

answered Jul 15 '13 at 22:40

Tim S.

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If it's as easy as this, I feel extremely stupid. Will try when I get back to work tomorrow, thanks. – ganders Jul 15 '13 at 22:47

score 0 · Answer 2 · answered Jul 15 '13 at 22:40

0

ApplicationCollection.Contains(r.Application)

answered Jul 15 '13 at 22:40

Steve0

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score 0 · Answer 3 · edited May 23 '17 at 10:25

0

Use .Contains(collection) instead of in. Here's a link since you wanted one.

edited May 23 '17 at 10:25

Community

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answered Jul 15 '13 at 22:41

TOlsen

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score 0 · Answer 4 · answered Jul 15 '13 at 23:00

If you want to write it the way you've shown, you can write this extension method:

public static bool In<T>(this T item, IEnumerable<T> set)
{
    return set.Contains(item);
}

And then use it exactly like you did in your question:

Application[] applicationCollection = GetAllApplications();
var result = repo.GetAll(r =>
    r.Email == myEmail &&
    r.Application.In(applicationCollection));

This will work fine if you're only working with in-memory sets. If you're doing something like LINQ-to-SQL, however, this won't be compatible.

Note: I'm not trying to imply that this extension method might be a good idea to use - I'm just saying it's possible to write one like that.

What's the syntax for this linq expression calling the in method

4 Answers4