Question

Does ExecuteScalar() have any advantages over ExecuteReader()?

Answer 1

ExecuteScalar only returns the first value from the first row of the dataset. Internal it is treated just like ExecuteReader(), a DataReader is opened, the value is picked and the DataReader gets destroyed afterwards. I also always wondered about that behavior, but it has one advantage: It takes place within the Framework…and you can’t compete with the Framework in manners of speed.

Edit By rwwilden:
Taking a look with Reflector inside SqlCommand.ExecuteScalar() you can see these lines:

SqlDataReader ds = this.RunExecuteReader(
    CommandBehavior.Default, RunBehavior.ReturnImmediately, true, "ExecuteScalar");
obj2 = this.CompleteExecuteScalar(ds, false);

Exactly what happens inside ExecuteReader. Another advantage is that ExecuteScalar returns null when no data is read. If you use ExecuteReader, you’d have to check this yourself.