C# send/recieve using serial port

C# send/recieve using serial port

I made serice aplication. I have data in lists. I communicate with more
device using COM1, COM2, etc.
I first list is COM port configuration and device id. In second is device
id and AT commands (more then one)
I need to go thrue first list and open ports one by one and send commands
from seconds list. When I send command I have to wait for recive some
second (depeng of command).
When I go to end i must repeat all process.
I try to make some code but without success.
Any idea, I will be grateful.
Thank you in advance.