How to ignore blank elements in linq query

Question

How to ignore blank elements in linq query

I have a linq query

            var usersInDatabase =
            from user in licenseUserTable
            where user.FirstName == first_name &&
             user.LastName == last_name 
            select user;

But if I get here and first_name or last_name is blank then I want to still evaluate the other data item.

Answer 1

    var usersInDatabase =
    from user in licenseUserTable
    select user;

    if (!string.IsNullOrEmpty(first_name)) { 
        usersInDatabase = usersInDatabase.Where(u => u.FirstName == first_name);
    }
    if (!string.IsNullOrEmpty(last_name)) { 
        usersInDatabase = usersInDatabase.Where(u => u.LastName == last_name);
    }

Answer 2

var usersInDatabase =
    from user in licenseUserTable
    where 
        (user.FirstName == first_name || first_name == string.Empty) &&
        (user.LastName == last_name || last_name == string.Empty)
    select user;

Now you will get records that match the first name given, if the first_name is empty all will match as long as it ALSO matches the last name, unless the last_name is blank as well. The only issue with this right now is that if first_name and last_name are blank, you will get everything.

Answer 3

This is the single-statement-style approach, but I find Mark's style much cleaner:

var usersInDatabase =
    from user in licenseUserTable
    where string.IsNullOrEmpty(first_name) || user.FirstName == first_name
    where string.IsNullOrEmpty(last_name) || user.LastName == last_name
    select user;