With aruduino, I am pretty sure you need to use the Serial.writeLN("Hello") Command.
and in vb.net you need to find out what comport your arduino is connected to.
then you csn set up a comport connection with serialPort and use that to communicate to the arduino.
here is a link with some serial comunication instructions for vb.net
Link to serial communications
Here is one for the Arduino side. LINK