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Thread Safe ObservableCollection in WPF

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Reference: http://stackoverflow.com/questions/2137769/where-do-i-get-a-thread-safe-collectionview

The following is an improvement on the implementation found by Jonathan. Firstly it runs each event handler on the dispatcher associated with it rather than assuming that they are all on the same (UI) dispatcher. Secondly it uses BeginInvoke to allow processing to continue while we wait for the dispatcher to become available. This makes the solution much faster in situations where the background thread is doing lots of updates with processing between each one. Perhaps more importantly it overcomes problems caused by blocking while waiting for the Invoke (deadlocks can occur for example when using WCF with ConcurrencyMode.Single).

 

using System;

using System.Collections.Generic;

using System.Collections.ObjectModel;

using System.Collections.Specialized;

using System.Linq;

using System.Text;

using System.Windows.Threading;

 

namespace ThreadSafeApplication.Helper

{

  public class ThreadSafeObservableCollection<T> : ObservableCollection<T>

  {

    public override event NotifyCollectionChangedEventHandler CollectionChanged;

    protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)

    {

      NotifyCollectionChangedEventHandler collectionChanged = this.CollectionChanged;

      if (collectionChanged != null)

        foreach (NotifyCollectionChangedEventHandler handler in collectionChanged.GetInvocationList())

        {

          DispatcherObject dispatcherObject = handler.Target as DispatcherObject;

          if (dispatcherObject != null)

          {

            Dispatcher dispatcher = dispatcherObject.Dispatcher;

            if (dispatcher != null && !dispatcher.CheckAccess())

            {

              dispatcher.BeginInvoke(

                  (Action)(() => handler.Invoke(this,

                      new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset))),

                  DispatcherPriority.DataBind);

              continue;

            }

          }

          handler.Invoke(this, e);

        }

    }

  }

}

 

 

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