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c#.netlinqlinq-to-sql

How to select only the records with the highest date in LINQ


I have a table, 'lasttraces', with the following fields.

Id, AccountId, Version, DownloadNo, Date

The data looks like this:

28092|15240000|1.0.7.1782|2009040004731|2009-01-20 13:10:22.000
28094|61615000|1.0.7.1782|2009040007696|2009-01-20 13:11:38.000
28095|95317000|1.0.7.1782|2009040007695|2009-01-20 13:10:18.000
28101|15240000|1.0.7.1782|2009040004740|2009-01-20 14:10:22.000
28103|61615000|1.0.7.1782|2009040007690|2009-01-20 14:11:38.000
28104|95317000|1.0.7.1782|2009040007710|2009-01-20 14:10:18.000

How can I, in LINQ to SQL, only get the last lasttrace of every AccountId (the one with the highest date)?


Solution

  • If you just want the last date for each account, you'd use this:

    var q = from n in table
            group n by n.AccountId into g
            select new {AccountId = g.Key, Date = g.Max(t=>t.Date)};
    

    If you want the whole record:

    var q = from n in table
            group n by n.AccountId into g
            select g.OrderByDescending(t=>t.Date).FirstOrDefault();