SQL Server connection string Asynchronous Processing=true

Question

I am using .Net 2.0 + SQL Server 2005 Enterprise + VSTS 2008 + C# + ADO.Net to develop ASP.Net Web application.

My question is, if I am using Asynchronous Processing=true with SQL Server authentication mode (not Windows authentication mode, i.e. using sa account and password in connection string in web.config), I am wondering whether Asynchronous Processing=true will impact performance of my web application (or depends on my ADO.Net code implementation pattern/scenario)? And why?

Answer 1

Begining with .NET Framework 4.5, Asynchronous Processing property is ignored, thus it's unnecessary to include it.

Quote:

Prior to .NET Framework 4.5, asynchronous programming with SqlClient was done with the following methods and the Asynchronous Processing=true connection property:

1. System.Data.SqlClient.SqlCommand.BeginExecuteNonQuery
2. System.Data.SqlClient.SqlCommand.BeginExecuteReader
3. System.Data.SqlClient.SqlCommand.BeginExecuteReader

This functionality remains in SqlClient in .NET Framework 4.5.

Beginning in the .NET Framework 4.5, these methods no longer require Asynchronous Processing=true in the connection string.

For more information, refer to below links:

• SqlConnectionStringBuilder.AsynchronousProcessing Property
• Asynchronous Programming

Answer 2

As a matter of fact, there are performance issues when you enable that option; see the ADO.NET 2.0 Asynchronous Command Execution (ASYNC) FAQ:

Q: What is the new ADO.NET 2.0 Asynchronous Command Execution feature.
A: ASYNC allows you to execute a command in a non-blocking manner. We are exposing in the SqlCommand the following asynchronous methods: BeginExecuteNonQuery, BeginExecuteReader and BeginExecuteXmlReader with polling, synchronization and (shudder) callbacks.

...

Q: So does this mean that every command I execute (sync or async) will happen in overlapped mode when I add ASYNC=TRUE to the connection string?
A: Yes it does, everything that we execute on this connection will be done in overlapped mode. For synchronous operations we internally wait for the completion before returning, we are basically faking the synchronous behavior on this connection. This is the reason why we require a connection string keyword.

Q: Does this have a perf impact?
A: Definitely, only use ASYNC=TRUE when you know that you are going to be using the async functionality.

...