How fast is LINQ?

Question

I need to manipulate 100,000 - 200,000 records.
I am thinking of using LINQ (to SQL) to do this.
I know from experience that filtering dataviews is very slow.
So

Answer 1

LINQ to SQL translates your query expression into T-SQL, so your query performance should be exactly the same as if you sent that SQL query via ADO.NET. There is a little overhead I guess, to convert the expression tree for your query into the equivalent T-SQL, but my experience is that this is small compared with the actual query time.

You can of course find out exactly what T-SQL is generated, and therefore make sure you have good supporting indexes.

The primary difference from DataViews is that LINQ to SQL does not bring all the data into memory and filter it there. Rather it gets the database to do what it's good at and only brings the matching data into memory.