CollectionView does not support changes to its source collection from a thread different from the dispatcher thread - caused from dispatcher thread

Question

I have an ObservableCollection, and an ICollectionView using the OC as a source:

private ObservableCollection<Comment> _Comments = new ObservableCollection<Comment>();
/// <summary>
/// Comments on the account
/// </summary>
[BsonElement("comments")]
public ObservableCollection<Comment> Comments
{
    get
    {
        return _Comments;
    }
    set
    {
        _Comments = value;
        OnPropertyChanged("Comments");
        OnPropertyChanged("CommentsSorted");
    }
}
private ICollectionView _CommentsSorted;
/// <summary>
/// Sorted list (reverse order) of the comments
/// </summary>
[BsonIgnore]
public ICollectionView CommentsSorted
{
    get
    {
        return _CommentsSorted;
    }
    set
    {
        _CommentsSorted = value;
        OnPropertyChanged("CommentsSorted");
    }
}

I have a command, which runs:

obj.Comments.Add(new Comment(Message));

where obj is an instance of the class containing the observable collection.

When calling this line, I am hitting the following exception:

System.NotSupportedException: 'This type of CollectionView does not support changes to its SourceCollection from a thread different from the Dispatcher thread.'

I have opened the Debug > Windows > Threads panel, and it is running on the main thread. I have tried putting it inside App.Current.Dispatcher.Invoke(...), no luck.

I can't figure out why this is happening. To make things stranger, I am able to run this fine, no problems at all, on another instance of the same class, which was created at the same time (returned and created together from my database in the same call). The first one I added a comment to no problem, and still can every time, yet all the others I have tried fail.

possible duplicate of [https://stackoverflow.com/questions/18331723/this-type-of-collectionview-does-not-support-changes-to-its-sourcecollection-fro](https://stackoverflow.com/questions/18331723/this-type-of-collectionview-does-not-support-changes-to-its-sourcecollection-fro) — mahlatse, Nov 23 '18 at 23:47
Did you find a solution to this? I've got the same problem and it's driving me crazy. — Neil B, Oct 12 '19 at 22:08
@NeilB I never found out what was happening, but in this situation I had 2 different listeners on the Changed event for the Comments. One was apparently unneeded and removing it seemed to solve this, though still not sure why etc. — pingu2k4, Oct 13 '19 at 23:37

Neil B · Accepted Answer · 2019-10-15T22:49:38.157

In my case the problem was that the collection view was refreshed in a task. Then later adding to the collection from the Main UI thread caused an exception.

When constructing the view model the collection was refreshed in a delayed task.

public MainVM()
{
    //other code...
    Task.Delay(100).ContinueWith(_ => UpdatePreferences());
}


public void UpdatePreferences()
{
    //other code..
    CollectionViewSource.GetDefaultView(Data.Customers).Refresh();
}

I was able to fix the problem by invoking the dispatcher.

Task.Delay(100).ContinueWith(_ => App.Current.Dispatcher.Invoke(()=> UpdatePreferences()));

That was the solution for my problem! – 10101 Jun 10 '20 at 09:43 — 10101, Jun 10 '20 at 09:43

score 0 · Answer 2 · answered Jan 05 '23 at 03:56

I had an issue where removing a item from an observable collection was throwing an error. "This type of CollectionView does not support changes to its SourceCollection from a thread different from the Dispatcher thread"

Dispatcher.Invoke(() =>
{
    ds.Remove(item);
});

My issue was calling this code from a different thread:

CollectionViewSource.GetDefaultView(ctlImagesGrid.ItemsSource).Refresh();

I assume, this forced the ItemsSource to be referenced from the calling thread. When I invoked this code from the main thread, modifying the observable collection had no errors.

 Dispatcher.Invoke(() =>
 {                         
  CollectionViewSource.GetDefaultView(ctlImagesGrid.ItemsSource).Refresh();
 });

CollectionView does not support changes to its source collection from a thread different from the dispatcher thread - caused from dispatcher thread

2 Answers2