Robin2 for your information: Arduino plugin is used for programming Arduino boards by Arduino Web Editor in place of Arduino IDE (desktop application).
From your Original Post it seems as if all you want to do is write a C# program that can receive data from an Arduino over a USB cable (serial connection) and save it to a MySQL database on your PC.
That should not be difficult to do. I don't use Windows myself (only Linux) so I am not familiar with C# but I'm sure it can do anything that Python can do.