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.)
Вопрос
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.
Решение
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.)
Другие советы
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;
}