asp.net mvc - Find records that were active in a certain date range using linq c# -

i need list records active in point in period of time:

the concept of active here range between dateactivation , datedeactivation.

model:

public class dme {     public datetime dateactivation { get; set; }               // set     public nullable<datetime> datedeactivation { get; set; }   // set or null } 

action:

public actionresult activerecordsintimeframe(string datestart, string datefinish) {     ilist<int> dmeids = db.dmes                         .asenumerable()                         .where(d => d.dateactivation >= convert.todatetime(datestart))                         .where(d => d.dateactivation <= convert.todatetime(datefinish))                         .where(d => d.datedeactivation == null || d.datedeactivation <= convert.todatetime(datefinish))                         .select(d => d.id).tolist();  } 

i not getting work properly, because can't records when dateactivation < datestart , datedeactivation null example, or when dateactivation > datestart , datedeactivation > datefinish

i think there 5 cases records active in time:

 dateactivation | datestart | datedeactivation  | datefinish   datestart | dateactivation | datedeactivation  | datefinish   datestart | dateactivation | datefinish | datedeactivation   dateactivation | datestart | datefinish | datedeactivation = null   datestart | dateactivation | datefinish | datedeactivation = null 

any please?

thanks.

i think should condition you're looking for:

(d.dateactivation == null || dtstart < d.datedeactivation) && dtend > d.dateactivation