Question

I have a Schedule class:

public class Schedule
{

 .....

 public DateTime? StartDate{get;set;}
 public DateTime? EndDate{get;set;}

 ....

}

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I would like to get the list of started Schedule objects from an IEnumerable list in the optimal way using linq or lambda.

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NOTE: An empty date value means infinity here. However, unspecified schedule period (empty start and end dates) means schedule is not started ..

Answer 1

schedules.Where(s => s.StartDate < DateTime.Now
                     || (s.StartDate == null && s.EndDate != null));

This assumes you actually want what you said – all started schedules, including those that already ended.

Also, you might want to change the way you represent unspecified schedule period, probably by adding a bool for that. If null means infinity, it should always mean infinity.