Question

Hi can you guys help me with this, I have try several things.
I need to search between two IEnumerables, here is the code.

IEnumerable<Project> Projects = new[] { new Project {id = "1", lan = "test1"},  new Project {id = "2", lan = "test1"}}

IEnumerable<string> lan = new [] { "test1", "test2"};
IEnumerable<string> indexFiltered = ?;

I need to do a linq query that return the Project.id thats have any Project.lan in lan.

Any idea?

Answer 1

Another efficient approach is using Enumerable.Join since it’s implemented as a hash table:

IEnumerable<string> indexFiltered = from p in Projects
                                    join l in lan on p.lan equals l
                                    select p.id;

Why is LINQ JOIN so much faster than linking with WHERE?

The Join operator takes the rows from the first tables, then takes only the rows with a matching key from the second table, then only the rows with a matching key from the third table.