On Aug 7, 2012, at 2:39 AM, Steven Pack <steven_john_p...@yahoo.com.au> wrote:
> and deleting the item:
>
> void DeleteItem(int position)
> {
> _log.Debug(Tag, "Deleting from position: " + position);
>
> var item = Headwords[position];
> Headwords.Remove(item);
>
> RefreshListView();
> }
>
>
> The DeleteItem method throws IndexOutOfRangeExceptions, firstly because it
> gets called multiple times and also because the position index doesn't
> actually represent the real index in the list somehow.
What is Headwords? What is Headword?
If I assume that Headwords is a List<Headword>, List<T>.Remove() [0] uses
List<T>.IndexOf() which uses Array.IndexOf() [1] which uses
EqualityComparer<T>.Equals(). If Headword doesn't implement
IEquatable<Headword>, then EqualityComparer<Headword> will in turn use
object.Equals(), which defaults to reference equality, which may or may not be
correct.
Furthermore, if you have the same Headword instance in Headwords multiple
times, List<T>.IndexOf() will return the _first_ index, which may not be the
index you want.
In any event, you should probably be using Headwords.RemoveAt(position), _not_
Headwords.Remove(Headwords[position]). The semantics are not equivalent between
those expressions if/when the same element is present multiple times in the
list.
- Jon
[0]
https://github.com/mono/mono/blob/master/mcs/class/corlib/System.Collections.Generic/List.cs#L501
[1]
https://github.com/mono/mono/blob/master/mcs/class/corlib/System/Array.cs#L2810
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