public List <string> GetModels(string brand)
{
var list = GPSCollection
.Where(t => t.Brand == brand).ToList();
return((from gps in list select gps.Model).Distinct().ToList());
}
public bool Exists(GPS gps)
{
return(GPSCollection.Where(t => t.DeviceID == gps.DeviceID).FirstOrDefault() != null);
}