Messagebox to show failure or success message

Question

Hi,

I am new on here and would like some help with dealing with what should be a simple task. I have a small form which is simply a data entry form for a single field (the second being a database autonumber). After running the SQL script I want either a messagebox to show that an entry already exists in the database or that the insert has been successful.

Below is my C# code.

Please can someone help as to how to achieve what I need! The above code obviously gives a successful message regardless of the real result.

Many thanks,