Please see the What are Presences article on a description on presences.
There are 2 ways to get presences (reads) from i4 Reader.
Using the GetPresences([spot_serial_number], out [presences dictionary]) SpotLib API method.
Dictionary<int, SpotLib.Presence> presences = new Dictionary<int, SpotLib.Presence>();
this.api.GetPresences(123, out presences);
This method will return a dictionary containing all presences for an individual i4 Reader.
The preferred way to get presences from the API is by subscribing to the "API.Presence" events, this way the "presence" events will be pushed to your application.
Subscribe to API.Presence events:
this.api.Presence += api_Presence;
Create an event handler for the events:
private bool SpotPresencesFilter(object presence)
PresenceEvent presenceEvent = (PresenceEvent)presence;
// Create logic to handle Presence events here!!
Please refer to the API Reference for a description of "PresenceEvent".