Can we have an example please?
Once you initialize it, it returns the USBC_CDC device which you can read/write to right away. IE to send a string:
USBC_CDC com1 = USBClientController.StandardDevices.StartCDC_WithDebugging();
byte[] buf = Encoding.UTF8.GetBytes("Hello, this is a test\r\n");
com1.Write(buf, 0, buf.Length);