Usinq Linq to select items that is in a semi-comma separated string?

Question

I have a string with semi-comma separated names:

string names = \"Jane;Harry\";

I also have a list of customer objects:

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Answer 1

Well, you should really split the string up to start with - otherwise you'll get a match for "Jane" even if the list is "Janet;Harry".

You could do:

string[] validNames = names.Split(';');
var query = customers.Where(c => validNames.Contains(c.FirstName));

Another option is to use a HashSet, which will perform a lot better when the list is very large:

HashSet validNames = new HashSet(names.Split(';'));
var query = customers.Where(c => validNames.Contains(c.FirstName));

I've used dot notation here instead of a query expression because it's simpler when you're just applying a clause or two. As a query expression though, it would be:

var query = from c in customers
            where validNames.Contains(c.FirstName)
            select c;