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// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
using System;
using System.Collections.ObjectModel;
namespace ICSharpCode.AvalonEdit.Utils
{
/// <summary>
/// A collection where adding and removing items causes a callback.
/// It is valid for the onAdd callback to throw an exception - this will prevent the new item from
/// being added to the collection.
/// </summary>
sealed class ObserveAddRemoveCollection<T> : Collection<T>
{
readonly Action<T> onAdd, onRemove;
public ObserveAddRemoveCollection(Action<T> onAdd, Action<T> onRemove)
{
this.onAdd = onAdd;
this.onRemove = onRemove;
}
protected override void ClearItems()
{
if (onRemove != null) {
foreach (T val in this)
onRemove(val);
}
base.ClearItems();
}
protected override void InsertItem(int index, T item)
{
if (onAdd != null)
onAdd(item);
base.InsertItem(index, item);
}
protected override void RemoveItem(int index)
{
if (onRemove != null)
onRemove(this[index]);
base.RemoveItem(index);
}
protected override void SetItem(int index, T item)
{
if (onRemove != null)
onRemove(this[index]);
try {
if (onAdd != null)
onAdd(item);
} catch {
// When adding the new item fails, just remove the old one
// (we cannot keep the old item since we already successfully called onRemove for it)
base.RemoveAt(index);
throw;
}
base.SetItem(index, item);
}
}
}
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