LINQ to SQL - Group By/Where

I'm trying to implement a group messaging feature in ASP.NET MVC. I want to display a list of all threads for a specific ContactID, displaying the latest message in that thread (no matter who it's from). I've set up my table as below:

MessageID ThreadID MessageBody ContactID 10000004 300152,300160, msg1 300160 10000005 300152,300160, msg2 300160 10000008 300152,300160, msg3 300152

I was able to display the latest message grouped by ThreadID. Ex:

ThreadID Count LatestMessage 300152,300160, 3 10000008

However, if I add the Where clause before the group by (see below), it'll filter on ContactID first before doing the group by, and producing this result:

ThreadID Count LatestMessage 300152,300160, 2 10000005

Here's the code:

var result = from s in pdc.Messages where s.ContactID == contactID group new { s } by new { s.ThreadID } into d let maxMsgID = d.Max(x => x.s.MessageID) select new { ThreadID = d.Key.ThreadID, Count = d.Count(item => item.s.MessageType == GlobalConstants.MessageTypeText), LastMessage = d.Where(x => x.s.MessageID == maxMsgID) };

Is there a way to do the group by and then filter on ContactID?

-------------Problems Reply------------

var result = from s in pdc.Messages
where s.ContactID == contactID
group new { s } by new { s.ThreadID } into d
select new {
ThreadID = d.Key,
Count = d.Count(item => item.s.MessageType == GlobalConstants.MessageTypeText),
LastMessage = d.select(x => x.s.MessageID).Max(),
};

Hope it can help you and have a nice day.

Category:linq to sql Views:0 Time:2010-11-15
Tags: linq to sql

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