LINQ Orderby Descending Query

I have a LINQ query that I want to order by the most recently created date.

I tried:

var itemList = from t in ctn.Items
                    where !t.Items && t.DeliverySelection
                    orderby t.Delivery.SubmissionDate descending
                    select t;

I have also tried:

var itemList = (from t in ctn.Items
                     where !t.Items && t.DeliverySelection
                     select t).OrderByDescending();

but this gives an error :

No overload for method 'OrderByDescending' takes 0 arguments

From what I've read, the first way it should work. I've tried changing descending to ascending just to see if it does anything开发者_如何学Go but it stays the same.

What am I doing wrong?

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You need to choose a Property to sort by and pass it as a lambda expression to OrderByDescending

like:

.OrderByDescending(x => x.Delivery.SubmissionDate);

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Really, though the first version of your LINQ statement should work. Is t.Delivery.SubmissionDate actually populated with valid dates?

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I think this first failed because you are ordering value which is null. If Delivery is a foreign key associated table then you should include this table first, example below:

var itemList = from t in ctn.Items.Include(x=>x.Delivery)
                    where !t.Items && t.DeliverySelection
                    orderby t.Delivery.SubmissionDate descending
                    select t;

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I think the second one should be

var itemList = (from t in ctn.Items
                where !t.Items && t.DeliverySelection
                select t).OrderByDescending(c => c.Delivery.SubmissionDate);

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Just to show it in a different format that I prefer to use for some reason: The first way returns your itemList as an System.Linq.IOrderedQueryable

using(var context = new ItemEntities())
{
    var itemList = context.Items.Where(x => !x.Items && x.DeliverySelection)
                                .OrderByDescending(x => x.Delivery.SubmissionDate);
}

That approach is fine, but if you wanted it straight into a List Object:

var itemList = context.Items.Where(x => !x.Items && x.DeliverySelection)
                                .OrderByDescending(x => x.Delivery.SubmissionDate).ToList();

All you have to do is append a .ToList() call to the end of the Query.

Something to note, off the top of my head I can't recall if the !(not) expression is acceptable in the Where() call.