How to create view model without sorting collections in memory.
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Chevex
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Published on 2011-01-13T22:04:24Z
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2011/01/14
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I have a view model (below).
public class TopicsViewModel
{
public Topic Topic { get; set; }
public Reply LastReply { get; set; }
}
I want to populate an IQueryable<TopicsViewModel>
with values from my IQueryable<Topic>
collection and IQueryable<Reply>
collection. I do not want to use the attached entity collection (i.e. Topic.Replies) because I only want the last reply for that topic and doing Topic.Replies.Last() loads the entire entity collection in memory and then grabs the last one in the list. I am trying to stay in IQueryable so that the query is executed in the database.
I also don't want to foreach through topics and query replyRepository.Replies because looping through IQueryable<Topic>
will start the lazy loading. I'd prefer to build one expression and have all the leg work done in the lower layers.
I have the following:
IQueryable<TopicsViewModel> topicsViewModel = from x in topicRepository.Topics
from y in replyRepository.Replies
where y.TopicID == x.TopicID
orderby y.PostedDate ascending
select new TopicsViewModel { Topic = x, LastReply = y };
But this isn't working. Any ideas how I can populate an IQueryable or IEnumerable of TopicsViewModel so that it queries the database and grabs topics and that topic's last reply? I am trying really hard to avoid grabbing all replies related to that topic. I only want to grab the last reply.
Thank you for any insight you have to offer.
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