Question

So, both ListBox.ObjectCollection and ListView.ListViewItemCollection implement the IList class, which provides Add and Remove methods but no AddRange, InsertRange, or RemoveRange. However, ListBox.ObjectCollection and ListView.ListViewItemCollection also provide an AddRange method — just no InsertRange or RemoveRange.

Look at the ArrayList class, on the other hand, which on top of implementing IList also provides AddRange, InsertRange, and RemoveRange. The same difference exists between the generic forms of this class and interface, List<T> (which has AddRange, InsertRange, and RemoveRange) and IList<T> (which only provides Add and Remove).

I can understand the IList and IList<T> interfaces not providing AddRange, etc. — it’s just an interface; anything beyond the minimum requirements of Add, Remove, RemoveAt, etc. is optional. But, given the usefulness of the *Range methods for the ArrayList and List<T> classes, and considering how handy they’d be for ListBox and ListView controls, I wonder why they don’t exist for these controls.

Does anyone know? Is there something about the internal implementation of InsertRange and RemoveRange that makes these methods somehow less efficient, more complicated, or otherwise less appropriate for ListBox.ObjectCollection and ListView.ListViewItemCollection than AddRange?

To be clear: I’m not looking for speculation of the “Looks like someone at Microsoft got lazy” variety; rather, I’m wondering if anyone actually knows of a legitimate difference between AddRange and InsertRange/RemoveRange that might explain the absence of these latter methods from ListBox.ObjectCollection and ListView.ListViewItemCollection.

Answer 1

1. In general it’s a pretty uncommon scenario to use InsertRange and (even more so) RemoveRange. Should RemoveRange, for example, remove the given range only if there is a continious range of elements similar to the given range, or should it remove the given elements one by one?

2. These methods are usually easy to implement if you need them. With the help of the extension methods you can have them to look almost like the native methods.

3. There are no signs in the code, showing that it would be complicated to implement those methods (just as thousands of other “useful” methods). Actually, the ListView implementation of InsertItems even takes an array of items already under the hood. Just the standard ListViewItemCollection.Insert() always provides array with 1 element. Take a look with the Reflector to the ListViewNativeItemCollection.Insert():

    public ListViewItem Insert(int index, ListViewItem item)
    {
        //Various checks excluded ....
        this.owner.InsertItems(index, new ListViewItem[] { item }, true);
        //More code excluded .....
        return item;
    }
   

I guess it just wasn’t that important to implement that feature… so they didn’t.

As Eric Lippert likes to say: “because no one ever designed, specified, implemented, tested, documented and shipped that feature”.