Question

consider the following code, which represents an attempt to implement partial matching. the intended result is a row for any 1 or more fields that match between the query entity and the data store.

so if you supply person.email we want a match against that, if you supply person.email and person.FirstName we should filter the results further, and so on.

        var results = from p in db.Persons
                      where p.CrookBookUserName.Trim().Contains(person.CrookBookUserName.Trim()) ||
                      p.email.Trim().Contains(person.email.Trim()) ||
                      p.FirstName.Trim().Contains(person.FirstName.Trim()) ||
                      p.LastName.Trim().Contains(person.LastName.Trim()) ||
                      p.phone.Trim().Contains(person.phone.Trim())
                      select p;

        return results;

unfortunately, this code always returns all rows in the db. why, and what should be the fix?

thanks in advance.

Answer 1

Does person have all fields populated? A p.email.Trim().Contains("") from an empty email address will return true for everything.

An extra (!String.IsNullOrEmpty(..)) && before each parameter, while verbose, will fix it if this is the problem.

Edit re comments:

Yeah, a helper method or something could help here… something like

public static bool ContainsIfNotEmptyTrimmed(this string source, string param)
{
    return !String.IsNullOrEmpty(param.Trim()) && source.Trim().Contains(param.Trim());
}

where p.CrookBookUserName.ContainsIfNotEmptyTrimmed(person.CrookBookUserName) || ...