1 files changed, 131 insertions, 0 deletions
diff --git a/Xamarin.Forms.Core/LockableObservableListWrapper.cs b/Xamarin.Forms.Core/LockableObservableListWrapper.cs
new file mode 100644
index 00000000..6bfdb39a
--- /dev/null
+++ b/Xamarin.Forms.Core/LockableObservableListWrapper.cs
@@ -0,0 +1,131 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Collections.Specialized;
+using System.ComponentModel;
+using System.Runtime.CompilerServices;
+using Xamarin.Forms.Internals;
+using Xamarin.Forms.Platform;
+
+namespace Xamarin.Forms.Internals
+{
+	public class LockableObservableListWrapper : IList<string>, ICollection<string>, INotifyCollectionChanged, INotifyPropertyChanged, IReadOnlyList<string>, IReadOnlyCollection<string>, IEnumerable<string>, IEnumerable
+	{
+		public readonly ObservableCollection<string> _list = new ObservableCollection<string>();
+
+		event NotifyCollectionChangedEventHandler INotifyCollectionChanged.CollectionChanged
+		{
+			add { ((INotifyCollectionChanged)_list).CollectionChanged += value; }
+			remove { ((INotifyCollectionChanged)_list).CollectionChanged -= value; }
+		}
+
+		event PropertyChangedEventHandler INotifyPropertyChanged.PropertyChanged {
+			add { ((INotifyPropertyChanged)_list).PropertyChanged += value; }
+			remove { ((INotifyPropertyChanged)_list).PropertyChanged -= value; }
+		}
+
+		public bool IsLocked { get; set; }
+
+		void ThrowOnLocked()
+		{
+			if (IsLocked)
+				throw new InvalidOperationException("The Items list can not be manipulated if the ItemsSource property is set");
+		}
+
+		public string this [int index] {
+			get { return _list [index]; }
+			set {
+				ThrowOnLocked();
+				_list [index] = value; }
+		}
+
+		public int Count {
+			get { return _list.Count; }
+		}
+
+		public bool IsReadOnly {
+			get { return ((IList<string>)_list).IsReadOnly; }
+		}
+
+		public void InternalAdd(string item)
+		{
+			_list.Add(item);
+		}
+
+		public void Add(string item)
+		{
+			ThrowOnLocked();
+			InternalAdd(item);
+		}
+
+		public void InternalClear()
+		{ 
+			_list.Clear();
+		}
+
+		public void Clear()
+		{
+			ThrowOnLocked();
+			InternalClear();
+		}
+
+		public bool Contains(string item)
+		{
+			return _list.Contains(item);
+		}
+
+		public void CopyTo(string [] array, int arrayIndex)
+		{
+			_list.CopyTo(array, arrayIndex);
+		}
+
+		public IEnumerator<string> GetEnumerator()
+		{
+			return _list.GetEnumerator();
+		}
+
+		public int IndexOf(string item)
+		{
+			return _list.IndexOf(item);
+		}
+
+		public void InternalInsert(int index, string item)
+		{
+			_list.Insert(index, item);
+		}
+
+		public void Insert(int index, string item)
+		{
+			ThrowOnLocked();
+			InternalInsert(index, item);
+		}
+
+		public bool InternalRemove(string item)
+		{
+			return _list.Remove(item);
+		}
+
+		public bool Remove(string item)
+		{
+			ThrowOnLocked();
+			return InternalRemove(item);
+		}
+
+		public void InternalRemoveAt(int index)
+		{
+			_list.RemoveAt(index);
+		}
+
+		public void RemoveAt(int index)
+		{
+			ThrowOnLocked();
+			InternalRemoveAt(index);
+		}
+
+		IEnumerator IEnumerable.GetEnumerator()
+		{
+			return ((IEnumerable)_list).GetEnumerator();
+		}
+	}
+}
+\ No newline at end of file