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MultipleActiveResultSets=True or multiple connections?

Posted by: admin November 29, 2017 Leave a comment

Questions:

I have some C# in which I create a reader on a connection (ExecuteReader), then for every row in that reader, perform another command (with ExecuteNonQuery). In this case is it better that I use MultipleActiveResultSets=True on my connection or use multiple connections?

Answers:

Multiple Active Result Sets (MARS) was added specifically for this type of operation so that you don’t have to have two connections open at the same time to be able to read from a SqlDataReader AND execute additional batches.

MARS is compatible with SQL Server 2005 and above. To quote from MSDN docs:

Before the introduction of Multiple
Active Result Sets (MARS), developers
had to use either multiple connections
or server-side cursors to solve
certain scenarios.

For more info see:

MSDN Library – MARS Overview

Worked example reading and updating data:

MSDN Library – Manipulating Data (MARS) scroll down to ‘Reading and Updating Data with MARS’

Questions:
Answers:

This is as far as I know the reason MARS was added, so yeah I think you should use it.

Questions:
Answers:

Best way to test this is to fire SQLServer Profiler, and see what really happens on the server side.

My guess is that it will not be better since you are using ExecuteNonQuery(). So, in fact, you don’t work with multiple results.