Sending data C# to PIC by using USB
Easiest way to send data from PC to your PIC device is using serial communication over USB.


Make your PIC act as USB CDC device.
To be recognized by OS and to provice a virtual COM port,

use a VID/PID combination that is used by some device that uses such serial over USB communcation and thus the standard serial driver
or add a custom driver (.inf file in Windows) for your device that then uses the standard serial driver (usbser.sys in Windows). Examples of such .inf file can be found in Microchip Application Libraries.

'Talk' to the device via the virtual COM port.

Use a serial console application (for example PuTTY) for manual testing.
Echo strings from console like echo hello pic >COM6.
Echo strings from an application/plugin/script/whatever to the virtual COM port.