improve usage of using blocks

[dmcgiv]

no need for separate using braces with the two adjacent using blocks
reader is disposable so should be in a using block

[alexkeh]

The purpose of adding braces is to make the sample code easily extensible. A developer can take the existing code without having to add the braces themselves, which they may not realize they need to do.

I can accept your DataReader using block change. Can you resubmit with the DataReader change only?

Also, Oracle requires code contributors to sign the Oracle Contributor Agreement (OCA) to protect our joint copyrights in the code. Can you accept the OCA and then re-submit with your name and email. More info on the OCA and what to do is here: https://github.com/oracle/dotnet-db-samples/blob/master/CONTRIBUTING.md

[alexkeh]

Closing the pull request since there's been no response for a month. Feel free to re-open and submit the modified change.