Good Day!
I have a lot of experience in creating of C based programs and system administration and I can help you to with your project.
But, I want to ask you several question about it:
If I understand you correctly, for a security reason you don`t want to open SQL server port to Internet.
Instead you want c# based application that will be installed like windows service that will connect to MS SQL server, do some query and send result throw Internet to you. Is it correct?
If so, how do you want to receive data? FTP, e-mail, TCP\IP client server based communication?...
When service should send data? By request via Internet, by timer, etc….?
How do you prefer to make query? Static query in source code, query from file, …?
Thank you.
And hope for future cooperation.