Question

Using:

• .Net 4.0

• EntityFramework 4.3

IF I query a DBSet in this manner:

public DbSet<Reciept> Reciepts { get; set; }
Reciepts.Where(rec =>rec.Number == reciept.Number &&
                        rec.Project.ID == reciept.Project.ID);

Will the entire table be returned, and THEN filterd by my query?

Or does it somehow translate this into SQL (Linq2SQL?), and return ONLY those rows?

Answer 1

It will only return filtered values.

You can always check the generated query by pointing a mouse cursor at a query variable while in debug:

var query = Reciepts.Where(rec =>rec.Number == reciept.Number && rec.Project.ID == reciept.Project.ID);
// put breakpoint here and stop mouse cursor at a 'query' variable

Another great tool which can be used to check what is really being sent to the DB is SQL Server Profiler (http://msdn.microsoft.com/en-us/library/ms187929.aspx). I use it all the time while developing with EF.