source: trunk/HeuristicLab.ExtLibs/HeuristicLab.AvalonEdit/5.0.1/AvalonEdit-5.0.1/Utils/ObserveAddRemoveCollection.cs @ 17530

// Copyright (c) 2014 AlphaSierraPapa for the SharpDevelop Team
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

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;
    
    /// <summary>
    /// Creates a new ObserveAddRemoveCollection using the specified callbacks.
    /// </summary>
    public ObserveAddRemoveCollection(Action<T> onAdd, Action<T> onRemove)
    {
      if (onAdd == null)
        throw new ArgumentNullException("onAdd");
      if (onRemove == null)
        throw new ArgumentNullException("onRemove");
      this.onAdd = onAdd;
      this.onRemove = onRemove;
    }
    
    /// <inheritdoc/>
    protected override void ClearItems()
    {
      if (onRemove != null) {
        foreach (T val in this)
          onRemove(val);
      }
      base.ClearItems();
    }
    
    /// <inheritdoc/>
    protected override void InsertItem(int index, T item)
    {
      if (onAdd != null)
        onAdd(item);
      base.InsertItem(index, item);
    }
    
    /// <inheritdoc/>
    protected override void RemoveItem(int index)
    {
      if (onRemove != null)
        onRemove(this[index]);
      base.RemoveItem(index);
    }
    
    /// <inheritdoc/>
    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);
    }
  }
}