I have a class that inherits from ObservableCollection
and adds a few additional methods such as AddRange
and RemoveRange
My base method call is this:
public void AddRange(IEnumerable<T> collection)
{
foreach (var i in collection) Items.Add(i);
OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
}
My problem with this is that I want to access e.NewItems
or e.OldItems
in the CollectionChanged
event to perform an action on whatever item is in the collection, and the NotifyCollectionChangedAction.Reset
action does not pass in these values
void Instances_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
if (e.NewItems != null) // e.NewItems is always null
{
foreach (var item in e.NewItems)
{
if (item is EventInstanceModel)
((EventInstanceModel)item).ParentEvent = this;
}
}
}
So I thought I could just use the NotifyCollectionChangedAction.Add
instead of Reset
, however that throws a Range actions are not supported
exception
public void AddRange(IEnumerable<T> collection)
{
var addedItems = collection.ToList();
foreach (var i in addedItems) Items.Add(i);
OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, addedItems));
}
So my question is, how can I raise a CollectionChanged event, and pass it the new or old item list?
I've been looking into it and apparently the CollectionChanged
method cannot be raised with multiple items.
So I can call
OnCollectionChanged(new NotifyCollectionChangedEventArgs(
NotifyCollectionChangedAction.Add, singleItem));
but I can't call
OnCollectionChanged(new NotifyCollectionChangedEventArgs(
NotifyCollectionChangedAction.Add, listOfItems));
For now what I have done is simply raise the Add event for every item added, but I am still rather unhappy at this since it means I raise the CollectionChanged
event for every item in the AddRange
method instead of only once.
public void AddRange(IEnumerable<T> collection)
{
foreach (var i in collection)
{
Items.Add(i);
OnCollectionChanged(new NotifyCollectionChangedEventArgs(
NotifyCollectionChangedAction.Add, i));
}
}