Slow foreach() on a LINQ query - ToList() boosts performance immensely - why is this?

Question

I kind of grasp the whole delayed execution concept, but the following has me puzzled...

On a DataTable containing about 1000 rows, I call AsEnumerable(). I

Answer 1

It will not get all items from database until you type

 ToList or First or Single

In foreach, you send a query into database for each item. So it works slower. Open your sql profiler to understand better.