Converting SQL CASE WHEN statement plus group statement into LINQ - sql-server

Question

How can I write in fluent linq syntax the "case when" sql statement?
select QueueItem, COUNT(*) as [Count],
SUM(CASE WHEN Queued = 0 THEN 1 ELSE 0 END) AS [Sent],
SUM(CASE WHEN Queued = 1 THEN 1 ELSE 0 END) AS Queued,
SUM(CASE WHEN Success = 1 THEN 1 ELSE 0 END) AS Exported,
SUM(CASE WHEN Success = 0 THEN 1 ELSE 0 END) AS Failed
from ExportQueue x
group by QueueItem
Is there some program that can convert SQL to LINQ? LinqPad maybe?

Answer 1

Ok, something like this. I'll need a bit of info to be sure though
Is Queued a bit? That makes a difference in linq where it doesn't in SQL.
I also don't know your context names but you should get the idea.
var query = Context.ExportQueues.Select(x => new {
QueueItem = x.QueueItem,
Sent = !x.Queued ? 1 : 0,
Queued = x.Queued ? 1 : 0,
Exported = x.Success ? 1 : 0,
Failed = !x.Success ? 1 : 0 })
.GroupBy(x => x.QueueItem)
.Select(g => new {
QueueItem = g.Key,
Sent = g.Sum(x => x.Sent),
Queued = g.Sum(x => x.Queued),
Exported = g.Sum(x => x.Exported),
Failed = g.Sum(x => x.Failed)
}).ToList();
EDIT You could also combine these by doing the case on the fly in the query. I always tend to write it out as above first as I work through it though as more complex aggregates can be a bit hard to debug if there's errors:
var query = Context.ExportQueues
.GroupBy(x => x.QueueItem)
.Select(g => new {
QueueItem = g.Key,
Sent = g.Sum(x => !x.Queued ? 1 : 0),
Queued = g.Sum(x => x.Queued ? 1 : 0),
Exported = g.Sum(x => x.Success ? 1 : 0),
Failed = g.Sum(x => !x.Success ? 1 : 0 )
}).ToList();

Answer 2

As an alternative to Gatts solution you can do something like
var query = Context.ExportQueues.
.GroupBy(x => x.QueueItem)
.Select(g => new {
QueueItem = g.Key,
Sent = g.Count(x=>!x.Queued),
Queued = g.Count(x => x.Queued),
Exported = g.Count(x => x.Success),
Failed = g.Count(x => !x.Failed)
}).ToList();

Answer 3

This is actually quite long-winded to write using LINQ. What you will need to do is to group first and then use lambda expressions to handle the aggregation. So something like:
from eq in ExportQueue
group eq by new {
eq.QueueItem
} into temp
select new {
temp.Key.QueueItem,
Agg1 = temp.Sum(n => n.Queued == 0 ? 1 : 0),
Agg2 = temp.Sum(n => n.Queued == 1 ? 1 : 0)
}
And so on, LinqPad will be really useful in trying to get this to work.