Check Reentrancy

gistfile1.cs

		[Serializable]
		private class SimpleMonitor : IDisposable
		{
			private int _busyCount;
			public bool Busy
			{
				get
				{
					return this._busyCount > 0;
				}
			}
			public void Enter()
			{
				this._busyCount++;
			}
			public void Dispose()
			{
				this._busyCount--;
			}
			[TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")]
			public SimpleMonitor()
			{
			}
		}
		private ObservableCollection<T>.SimpleMonitor _monitor = new ObservableCollection<T>.SimpleMonitor();

		protected IDisposable BlockReentrancy()
		{
			this._monitor.Enter();
			return this._monitor;
		}

		protected void CheckReentrancy()
		{
			if (this._monitor.Busy && this.CollectionChanged != null && this.CollectionChanged.GetInvocationList().Length > 1)
			{
				throw new InvalidOperationException(SR.GetString("ObservableCollectionReentrancyNotAllowed"));
			}
		}

		protected virtual void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
		{
			if (this.CollectionChanged != null)
			{
				using (this.BlockReentrancy())
				{
					this.CollectionChanged(this, e);
				}
			}
		}

		protected override void RemoveItem(int index)
		{
			this.CheckReentrancy();
			T t = base[index];
			base.RemoveItem(index);
			this.OnPropertyChanged("Count");
			this.OnPropertyChanged("Item[]");
			this.OnCollectionChanged(NotifyCollectionChangedAction.Remove, t, index);
		}
		protected override void InsertItem(int index, T item)
		{
			this.CheckReentrancy();
			base.InsertItem(index, item);
			this.OnPropertyChanged("Count");
			this.OnPropertyChanged("Item[]");
			this.OnCollectionChanged(NotifyCollectionChangedAction.Add, item, index);
		}