How to read serial port control line states with .net

I'开发者_开发技巧m working on a project where I need to trigger an event when a switch is closed. It is my understanding that it is possible to use the control lines on a serial port and read whether the switch is closed or not. I've found a schematic of how to connect the switches to the pins, but I have not been able to find any example code on how you can read the state of the switches.

The schematic is located here: http://irtel.uni-mannheim.de/pxlab/doc/manual/Devices.html

Anyone have any ideas how you could use vb.net or C# to read the state of the switch on one of these control lines?

A pin changed event handler might help

Dim WithEvents sp As New IO.Ports.SerialPort
Private Sub sp_PinChanged(sender As Object, _
                          e As System.IO.Ports.SerialPinChangedEventArgs) Handles sp.PinChanged
    'look at e.EventType or check states
    Select Case True
        Case sp.CDHolding
        Case sp.CtsHolding
        Case sp.DsrHolding
        Case sp.RtsEnable
        Case e.EventType = IO.Ports.SerialPinChange.Ring
    End Select
End Sub

This assumes that the port is open.

edit: To detect ring you have to use e.EventType.

This should help you get started: http://msdn.microsoft.com/en-us/library/system.io.ports.serialport.aspx. There are good serial tutorials there too.