Question

Here’s my setup.

public class ItemList : List<Item>
{
  public void Load() {...}
  public void Save() {...}
}

Load reads from an XML file to populate the ItemList

I then attempt to order the item list by a Priority. This is an int? For the test purposes however all the items have a different value.

ItemList itemList = new ItemList();
itemList.Load();

ItemList newItemList = itemList
                        .OrderBy(item => item.Priority) as ItemList;

return newItemList;

In the above newItemList is always null. itemList has a Count of 7. I’ve triple checked and all the items in the itemList instance have a priority set.

What am I doing wrong?

I’ve also tried…

ItemList newItemList = itemList
                        .OrderBy(item => item.Priority)
                        .ToList() as ItemList;

Nothing seems to be working.

Thanks in advance!

Answer 1

Neither OrderBy or ToList returns an ItemList, so the casting returns null, as Joseph pointed out.

As you are inheriting from the List<T> class, you can just use the Sort method to sort it:

ItemList itemList = new ItemList();
itemList.Load();
itemList.Sort((x, y) => x.Priority.CompareTo(y.Priority));
return itemList;