CODEWITHSUNDEEP
c#linq-to-entitieslinq-expressions
user2324540
user2324540

Reputation:

Building a lambda expression using concatenation

Let's say I have these two entities :

Then, consider this expression, in which d represents a Document and p represents a Period, that is used to filter a Document collection to return only those who are part of a given Period :

d => d.Date >= p.DateFrom && d.Date <= p.DateTo

The problem is, given a collection of Period entities, how could I build a lambda expression which represents a concatenation of multiple expressions like the above expression, so it gives :

d => 
     (d.Date >= p1.DateFrom && d.Date <= p1.DateTo) 
  && (d.Date >= p2.DateFrom && d.Date <= p2.DateTo) 
  && (d.Date >= p3.DateFrom && d.Date <= p3.DateTo) 
  && ...

I want the result to be a lambda expression that I can further combine to other conditions before filtering my Document collection.

Upvotes: 1

Views: 578

Answers (2)

dinony
dinony

Reputation: 624

Assuming the collection of period entities (periods) is available for the lambda expression:

(d) => 
{ 
   bool cond = false;
   foreach(Period p in periods)  
   {
      // check period
      // return earlier if condition not met
   }

   return cond;
}

Upvotes: 0

Servy
Servy

Reputation: 203829

var documentsInAllPeriods = documents.Where(d => periods.All(p => 
    d.Date >= p.DateFrom && d.Date <= p.DateTo));

(Note you can change All to Any if you want the documents in any period rather than the documents in every period.)

Upvotes: 4

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