c# bindingoperations.enablecollectionsynchronization(environmenterrors, - This type of CollectionView does not support changes to its SourceCollection from a thread different from the Dispatcher thread




_lock); doesn (6)

In my case (I populate ObservableCollection with asynchronous tasks and do not have access to App instance) I use TaskScheduler.FromCurrentSynchronizationContext() to cleanup the collection on faulted:

        // some main task
        Task loadFileTask = Task.Factory.StartNew(...);

        Task cleanupTask = loadFileTask.ContinueWith(
            (antecedent) => { CleanupFileList(); },
            /* do not cancel this task */
            CancellationToken.None,
            /* run only if faulted main task */
            TaskContinuationOptions.OnlyOnFaulted,
            /* use main SynchronizationContext */
            TaskScheduler.FromCurrentSynchronizationContext());

I have a DataGrid which is populating data from ViewModel by asynchronous method.My DataGrid is :

<DataGrid ItemsSource="{Binding MatchObsCollection}"  x:Name="dataGridParent" 
                      Style="{StaticResource EfesDataGridStyle}" 
                      HorizontalGridLinesBrush="#DADADA" VerticalGridLinesBrush="#DADADA" Cursor="Hand" AutoGenerateColumns="False" 
                      RowDetailsVisibilityMode="Visible"  >

I am using http://www.amazedsaint.com/2010/10/asynchronous-delegate-command-for-your.html to implement asynchronous way in my viewmodel.

Here is my viewmodel code:

public class MainWindowViewModel:WorkspaceViewModel,INotifyCollectionChanged
    {        

        MatchBLL matchBLL = new MatchBLL();
        EfesBetServiceReference.EfesBetClient proxy = new EfesBetClient();

        public ICommand DoSomethingCommand { get; set; }
        public MainWindowViewModel()
        {
            DoSomethingCommand = new AsyncDelegateCommand(
                () => Load(), null, null,
                (ex) => Debug.WriteLine(ex.Message));           
            _matchObsCollection = new ObservableCollection<EfesBet.DataContract.GetMatchDetailsDC>();                

        }       

        List<EfesBet.DataContract.GetMatchDetailsDC> matchList;
        ObservableCollection<EfesBet.DataContract.GetMatchDetailsDC> _matchObsCollection;

        public ObservableCollection<EfesBet.DataContract.GetMatchDetailsDC> MatchObsCollection
        {
            get { return _matchObsCollection; }
            set
            {
                _matchObsCollection = value;
                OnPropertyChanged("MatchObsCollection");
            }
        }        
        //
        public void Load()
        {            
            matchList = new List<GetMatchDetailsDC>();
            matchList = proxy.GetMatch().ToList();

            foreach (EfesBet.DataContract.GetMatchDetailsDC match in matchList)
            {
                _matchObsCollection.Add(match);
            }

        }

As you can see in my Load() method in my ViewModel first I am getting matchList (which is a list of a DataContract Class) from my Service.Then by foreach loop I am inserting my matchList items to my _matchObsCollection(which is an ObservableCollection of DataContract Class)).Now here I am getting the above error (as I shown in Title) "This type of CollectionView does not support changes to its SourceCollection from a thread different from the Dispatcher thread"

Can anyone suggest me any solution.Moreover if possible I would like to know how to bind my DataGrid in View and also refresh it asynchronously if any better way is there.


Since your ObservableCollection is created on UI thread, you can only modify it from UI thread and not from other threads. This is termed as thread affinity.

If you ever need to update objects created on UI thread from different thread, simply put the delegate on UI Dispatcher and that will do work for you delegating it to UI thread. This will work -

    public void Load()
    {
        matchList = new List<GetMatchDetailsDC>();
        matchList = proxy.GetMatch().ToList();

        foreach (EfesBet.DataContract.GetMatchDetailsDC match in matchList)
        {
            App.Current.Dispatcher.Invoke((Action)delegate // <--- HERE
            {
                _matchObsCollection.Add(match);
            });
        }
    }


You can do this:

App.Current.Dispatcher.Invoke((System.Action)delegate
             {
               _matchObsCollection.Add(match)
             });

For .NET 4.5+: You can follow the answer of Daniel. In his example you give the responsability to the publisher that they need to call or invoke on the correct thread:

var uiContext = SynchronizationContext.Current;
uiContext.Send(x => _matchObsCollection.Add(match), null);

Or you could put the responsability to your service/viewmodel/whatever and simply enable CollectionSynchronization. This way if you make a call you don't have to worry on which thread you are on and on which one you make the call. The responsability is not for the Publisher anymore. (This may give you a little performance overhead but doing this in a central service, it can save you a lot of exceptions and gives you easier application maintenance.)

private static object _lock = new object();

public MainWindowViewModel()
{
    // ...
    _matchObsCollection = new ObservableCollection<EfesBet.DataContract.GetMatchDetailsDC>();
    BindingOperations.EnableCollectionSynchronization(_matchObsCollection , _lock);
} 

More info: https://msdn.microsoft.com/en-us/library/system.windows.data.bindingoperations.enablecollectionsynchronization(v=vs.110).aspx

In Visual Studio 2015 (Pro) go to Debug --> Windows --> Threads to easily debug and see on which threads you are on.


If you are using BackgroundWorker you should raise the event in the same thread of the UI.

For i.e. if you have two views A and B and the following code inside A raises the event WakeUpEvent

//Code inside codebehind or viewmodel of A
    var worker = new BackgroundWorker();
    worker.DoWork += WorkerDoWork; //<-- Don't raise the event WakeUpEvent inside this method
    worker.RunWorkerCompleted += workerRunWorkerCompleted; // <-- Raise the event WakeUpEvent inside this method instead
    worker.RunWorkerAsync();

//Code inside codebehind or viewmodel of view B
    public ViewB () {
        WakeUpEvent += UpdateUICallBack;
    }
    private void UpdateUICallBack() {
        //Update here UI element
    }

The WorkerDoWork method is executed in a thread that is not the same of the UI.


On .NET 4.5 The maximum instantiatable length of a byte array is: 2147483591, or 56 less than int.MaxValue. Found via:

for (int i = int.MaxValue; i > 0; i--)
{
    try
    {
        byte[] b = new byte[i];
        Console.Out.WriteLine("MaxValue: " + i);
        Environment.Exit(0);
    }
    catch (Exception ignored)
    {}
}






c# wpf xaml silverlight mvvm