Question

I need to modify a collection so that I can sort the sequence of items in it.

So I am doing something like:

IEnumerable<ItemType> ordered = myItems.OrderBy( (item) => item.Age);

However, I want to modify the myItems collection itself to have the ordered sequence… is it possible?

I want something like:

myItems.SomeActionHere // This should modify myItems in place.

This might be a newbie or noob question. Sorry about that.

Answer 1

If it’s an array you can use Array.Sort. This performs an in-place sort without duplicating references/values.

Equally, however, you can just tag .ToArray() or .ToList() to the end of your linq statement to ‘realise’ the ordered enumerable if duplicating references is not an issue (normally it isn’t).

E.g:

myItems = myItems.OrderBy(i => i.Age).ToArray();

If you absolutely need it back as another ReadOnlyCollection instance – you could do this:

myItems = new ReadOnlyCollection<ItemType>(myItems.OrderBy(i => i.Age).ToArray());

Note that .ToArray() works because arrays implement IList<T> even though they’re not modifiable.

Alternatively – there’s also Array.AsReadOnly – to turn it on it’s head:

myItems = Array.AsReadOnly(myItems.OrderBy(i => i.Age).ToArray());

Apart from being a shorter line of code I don’t see much benefit – unless reducing angle-brackets is important to you 🙂