Question

Another question regarding EF:

I was wondering what’s going behind the scenes when iterating over a query result.

For example, check out the following code:

var activeSources = from e in entitiesContext.Sources
                    where e.IsActive
                    select e;

and then:

foreach (Source currSource in allSources)
{
   code based on the current source...
}

Important note: Each iteration takes a while to complete (from 1 to 25 seconds).

Now, I assume EF is based on DataReaders for maximum efficiency, so based on that assumption, I figure that in the above case, the Database connection will be kept open until I finish iterating over the results, which will be a very long time (when talking in terms of code), which is something I obviously don’t want.

Is there a way to fetch the entire data like I would’ve done with plain old ADO.NET DataAdapters, DataSets and the fill() method instead of using DataReaders?

Or maybe i’m way off with my assumptions?

In any case I would’ve loved to be pointed to a good source explaining this if available.

Thanks,

Mikey

Answer 1

If you want to get all of the data up front, similar to Fill(), you need to force the query to execute.

var activeSources = from e in entitiesContext.Sources
                    where e.IsActive
                    select e;

var results = activeSources.ToList();

After ToList() is called you will have the data and be disconnected from the database.