Question

I’m having a debate with another programmer I work with.

For a database return type, are there any significant memory usage or performance differences, or other cons which should make someone avoid using the DataSets and DataTables and favour types which implement IEnumerable<T>… or vice versa

I prefer returning types which implementIEnumerable<T> (List<T>, T[] etc) because it’s more lightweight, strongly typed to the object when accessing properties, allows richer information about the underlying type etc. They do take more time to set up though when manually using the data reader.

Is the only reason to use DataTables these day just lazyness?

Answer 1

DataTables are definitely much heavier than Lists, both in memory requirements, and in processor time spent creating them / filling them up.
Using a DataReader is considerable faster (although more verbose) than using DataTables (I’m assuming you’re using a DataAdapter to fill them).

That said…
Unless this is in some place where it really matters, you’re probably fine either way, and both methods will be fast enough, so just go with whatever is more comfortable in each case. (Sometimes you want to fill them up with little code, sometimes you want to read them with little code)

I myself tend to only use DataTables when I’m binding to a GridView, or when I need more than one resultset active at the same time.