Interacting with Dallas IButton form C#

Question

 

Hi All,

Can any one help me how to interact with Dallas IButton, how to recognise whether the button is present or not and read the data from the iButton, my requirement is to allow the user to login to the application if the IButton is present and valid, logout the user once the ibutton is removed from the slot.

Note: the iButton is a physical device for the user

Thanks in advance
Krishna