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Q&A Order a subcollection from linq

I am using linq/EF core to retrieve data via an API call. How do I sort the collection of related data for each retrieved entity? Assume the following structure: an Order is made on a certain da...

1 answer  ·  posted 2y ago by mcalex‭  ·  last activity 2y ago by Alexei‭

#1: Initial revision by user avatar mcalex‭ · 2022-06-08T08:03:13Z (about 2 years ago)
Order a subcollection from linq
I am using linq/EF core to retrieve data via an API call.

How do I sort the collection of related data for each retrieved entity?

Assume the following structure:  an Order is made on a certain date, and is comprised of (inter alia) a collection of OrderLines, where an OrderLine comprises a Product and a quantity. 

How do I generate a list of Orders sorted by OrderDate, with the OrderLines for each Order displayed in Alphabetical order by Product?

I have tried:

```
context.TblOrder
    .Include(o => o.TblOrderLine
        .OrderBy(ol => ol.ProductName))
    .OrderBy(o => o.OrderDate);
```

But when I try to send that to a list, I get an `Expression of type 'System.Linq.IOrderedQueryable1<T> cannot be used for return type 'System.Linq.IOrderedEnumerable1<T>`

I also tried to retrieve (correctly sorted) OrderDetails separately as a DbSet<OrderDetail> (ie same as the context), but then I couldn't link them through the navigation property.

```
var lines = context.TblOrderLine
    .OrderBy(ol => ol.ProductName) as DbSet<TblOrderLine>;

context.TblOrders
    .Include(o => o.lines)
    .OrderBy(o => o.OrderDate);
```

`TblOrder does not contain a definition for lines and no accessible extension method ... could be found`.

How do I retrieve data with a correctly sorted sub-collection of data for each record?