I have a L2S repository query which I'm stuggling to write in a nice way. It looks something like...
_orderRepository
.GetAllByFilter(o => o.CustomerId == id)
.Select(o =>
new CustomerOrderRecord
(
o.Id,
o.PartNumber,
o.Date
// ... etc, more order details
/* Here I need the last DateTime? the customer placed
an order for this item, which might be null.
So I end up with the following horrible part of
the query */
o.Customer.CustomerOrderRecords
.Where(x => x.PartNumber == o.PartNumber)
.OrderByDescending(x => x.Date).FirstOrDefault()
== null ? null :
o.Customer.CustomerOrderRecords
.Where(x => x.PartNumber == o.PartNumber)
.OrderByDescending(x => x.Date).First().Date;
)).ToList();
So hopefully you can see the problem that I'm having to write the whole query chain twice just to do the null check when receiving the LastOrdered
value.
This needs to be written in-line (I think) because GetAllByFilter
returns an IQueryable
.
I tried to use an intermediate variable within the select statement, so I'd have something a bit like the following, but I couldn't get anything like that to compile.
.Select(o =>
new CustomerOrderRecord
(
o.Id,
o.PartNumber,
o.Date
// ... etc, more order details
var last = o.Customer.CustomerOrderRecords
.Where(x => x.PartNumber == o.PartNumber)
.OrderByDescending(x => x.Date).FirstOrDefault()
== null ? null : last.Date;
)).ToList();
Is there a syntax trick available which solves this problem?
Try using Select
to fetch the Date
member:
o.Customer.CustomerOrderRecords
.Where(x => x.PartNumber == o.PartNumber)
.OrderByDescending(x => x.Date)
.Select(x => (DateTime?)x.Date)
.FirstOrDefault()
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