How to get a list which contains at least all the values of another list?

Question

I have the situation where a list must contains at least the values of another list. So imagine we have list A with values 1, 2, 3. This is the list with the required values.

List B has the values 1, 5, 6, 7
List C has the values 1, 2, 3, 4, 7
List D has the values 2, 5, 6

In this situation I only want List C, since this is the only list which contains the values 1, 2 end 3.

I've tried this, but this doesn't work since it is always true:

query = from doc in query
        let tagIds = from t in doc.Tags select t.Id
        where parameters.TagIds.Except(tagIds).Count() <= parameters.TagIds.Count()
        select doc;

And when using this:

 query = from doc in query
        let tagIds = from t in doc.Tags select t.Id
        where !parameters.TagIds.Except(tagIds).Any<int>()
        select doc;

I only get the lists where the list matches exactly the 'required' list.

My question is, how can I solve my situation in a Linq 2 SQL query?

Answer 1

Try

var query = from doc in query
            let tagIds = from t in doc.Tags select t.Id
            where parameters.All(p => tagIds.Contains(p))
            select doc;

Answer 2

Try this link

Does .NET have a way to check if List a contains all items in List b?

here you can run the same above method in all available lists.

public static bool ContainsAllItems(List<T> a, List<T> b)
{
    return !b.Except(a).Any();
}

This checks whether there are any elements in b which aren't in a - and then inverts the result.