Can I get the current logged in Zoho User Details?

Can I get the current logged in Zoho User Details?

Hi,
I am developing a C#.Net Sales Board and need to know the salesperson currently logged in when they view the board site to retrieve their ID, team, and other custom fields from their CRM user module.
I have successfully setup my .Net app to connect to Zoho CRM but the currentuser is always my account, regardless of who is logged in (I am the user who requested the grant and refresh token).  How do I find the zoho user who is logged into the browser?  and if they are not logged in to redirect them to log in? (like when their session times out for other zoho apps)?
Thanks!
Alex.