I have two Generic Lists containing different types, for the sake of example, lets call them Products
and Employees
. I'm trying to find Products that are based at the same location as Employees, i.e. where product.SiteId == emp.SiteId
List<Product> lstProds;
List<Employees> lstEmps;
My (old skool) brain is telling me to use a forEach
loop to find the matches but I suspect there is a ('better'/terser/faster?) way to do it using Linq. Can anyone illuminate me? All the examples I've found online deal with Lists of primitives (strings/ints) and are not especially helpful.
I would say:
var products = from product in lstProds
join employee in lstEmps on product.SiteId equals employee.SiteId
select product;
However, if there are multiple employees with the same site ID, you'll get the products multiple times. You could use Distinct
to fix this, or build a set of site IDs:
var siteIds = new HashSet<int>(lstEmps.Select(emp => emp.SiteId));
var products = lstProds.Where(product => siteIds.Contains(product.SiteId));
That's assuming SiteId
is an int
- if it's an anonymous type or something similar, you may want an extra extension method:
public static HashSet<T> ToHashSet<T>(this IEnumerable<T> source)
{
return new HashSet<T>(source);
}
Then:
var siteIds = lstEmps.Select(emp => emp.SiteId).ToHashSet();
var products = lstProds.Where(product => siteIds.Contains(product.SiteId));
Alternatively, if you have few employees, this will work but is relatively slow:
var products = lstProds.Where(p => lstEmps.Any(emp => p.SiteId == emp.SiteId));
Add a ToList
call to any of these approaches to get a List<Product>
instead of an IEnumerable<Product>
.