Question

Dapper implicitly expects a connection to be open when it uses it. Why doesn’t it open and close it itself? Wouldn’t this simply connection management?

I ask because a co-worker and I have been going back and forth on the nature of what goes on behind the scenes with connection pooling, and if there is any benefit to keeping a connection open amongst multiple commands, or to open and close it for each command.

Answer 1

Dapper now (and for quite some time) deals with this internally. It just works™

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Original (outdated) answer:

You aren’t wrong. The reason I hadn’t noticed this inconvenience is that for legacy reasons (specifically: we used to use LINQ-to-SQL exclusively) our primary connection-like-thing is a DataContext – so we re-expose the dapper methods as extension methods on DataContext.

The silly thing is: what these methods do is:

using(db.Connection.EnsureOpen()) {
    db.Connection.{the dapper method}
}

Here EnsureOpen is a cheeky method that:

• if the connection is open, returns null
• otherwise, it opens the connection, and returns an IDisposable token that closes the connection when done

So: we obviously felt exactly your pain, but we implemented it a layer further up.

Please log this as a feature request. We have all the code (although I’ll need to tweak it slightly to fit the “reader” for non-buffered data) – there’s absolutely no reason that dapper can’t take ownership of this.