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Grauenwolf opened this issue Dec 4, 2018 · 10 comments · May be fixed by #9568 or #10845
Open

Improved INotifyCollectionChanged Handling #52

Grauenwolf opened this issue Dec 4, 2018 · 10 comments · May be fixed by #9568 or #10845
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🚧 work in progress Enhancement Requested Product code improvement that does NOT require public API changes/additions Performance Performance related issue
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Future

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@Grauenwolf
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This is a carry over from .NET Framework.

If INotifyCollectionChanged.CollectionChanged -> NotifyCollectionChangedEventArgs.NewItems has more than one item, most WPF controls will throw an exception.

The main reason for this original design is that ObservableCollection doesn't have an AddRange method and the controls assum that nothing else will support INotifyCollectionChanged.
@dotMorten
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Yes! This has been extremely annoying. Being able to trigger one large change for a set of items without causing UI relayout over and over again would be a huge perf improvement. The interface completely supports this, but for some reason WPF never has. Currently our only choice is to trigger a reset event, which causes a complete relayout of all items.

@benaadams
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benaadams commented Dec 4, 2018 •
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The main reason for this original design is that ObservableCollection doesn't have an AddRange method

The following apis have been approved for Collection<T> and ObservableCollection<T> in .NET Core; though not implemented yet https://github.com/dotnet/corefx/issues/10752:

public partial class Collection<T>
{
    public void AddRange(IEnumerable<T> collection);
    public void InsertRange(int index, IEnumerable<T> collection);
    public void RemoveRange(int index, int count);
    public void ReplaceRange(int index, int count, IEnumerable<T> collection);

    // These are override by ObservableCollection<T> to raise the event:
    protected virtual void InsertItemsRange(int index, IEnumerable<T> collection);
    protected virtual void RemoveItemsRange(int index, int count);
    protected virtual void ReplaceItemsRange(int index, int count, IEnumerable<T> collection);
}

@dotMorten
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The main reason for this original design is that ObservableCollection doesn't have an AddRange method

This isn't about ObservableCollection, but about INotifyCollectionChanged interface. Any collection can implement that interface and have add-range, or be adding items in "chunks" (like incrementally loading datasources etc)

@airbreather
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airbreather commented Dec 4, 2018 •
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most WPF controls will throw an exception.

I was under the impression that it's "just" System.Windows.Data.CollectionView which would need to change, and that (in theory) something else could implement System.ComponentModel.ICollectionView to get the desired benefits.

Admittedly, however, I haven't tried it... am I mistaken?

Edit: that said, System.ComponentModel.ICollectionView itself extends System.Collections.Specialized.INotifyCollectionChanged, which makes me think that System.Windows.Data.CollectionView is likely to be just the most visible of, perhaps, many places that don't support batched changes...

@rladuca rladuca added the Enhancement Requested Product code improvement that does NOT require public API changes/additions label Dec 4, 2018
@rladuca rladuca added this to the Future milestone Dec 4, 2018
@TheSylence TheSylence mentioned this issue Mar 14, 2020
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@michael-hawker michael-hawker mentioned this issue Mar 30, 2021
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@YZahringer
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Could be a 6.0.0 candidate? This currently blocks the range support in .net 6 ObservableCollection

This was referenced Oct 20, 2021
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@DamirLisak
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In this context, I would like to point out the following problem:
dotnet/efcore#12675
EF core uses ObservableHashSet that implements INotifyCollectionChanged. However, the ObservableHashSet is an unsorted collection and is not able to specify an index in the OldStartingIndex property for a Remove action. This leads to an exception at this point in the EnumerableCollectionView.cs:

wpf/src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/Data/EnumerableCollectionView.cs

Line 423 in 026f338

case NotifyCollectionChangedAction.Remove:

In this case, the entire CollectionView would have to be reloaded.

@symbiogenesis
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symbiogenesis commented Jan 26, 2024 •
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This is one of the top-requested features in all of the world of .NET, going back many years. Offering this is crucial.

@dotMorten
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dotMorten commented Jul 5, 2024 •
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Suggestion: We don't we log an issue for each control that have a problem with multi-item changes, and that way we can start chipping away at it and hopefully get to a point where we can add AddRange to ObservableCollection<T> ? This issue could then be the epic for the individual tasks.

@symbiogenesis
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@anjali-wpf @singhashish-wpf

@symbiogenesis
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@robertmclaws

@rchauhan18 rchauhan18 added the Performance Performance related issue label Jul 30, 2024
@Mrxx99 Mrxx99 linked a pull request Aug 13, 2024 that will close this issue
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@Sergio0694 Sergio0694 linked a pull request May 12, 2025 that will close this issue
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@benaadams @dotMorten @symbiogenesis @airbreather @YZahringer @Grauenwolf @DamirLisak @rladuca @rchauhan18
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