source: branches/PersistenceOverhaul/HeuristicLab.ExtLibs/HeuristicLab.NRefactory/5.5.0/NRefactory-5.5.0/Utils/CallbackOnDispose.cs

// Copyright (c) 2010-2013 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
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using System;
using System.Diagnostics;
using System.Threading;

namespace ICSharpCode.NRefactory.Utils
{
  /// <summary>
  /// Invokes an action when it is disposed.
  /// </summary>
  /// <remarks>
  /// This class ensures the callback is invoked at most once,
  /// even when Dispose is called on multiple threads.
  /// </remarks>
  public sealed class CallbackOnDispose : IDisposable
  {
    Action action;
    
    public CallbackOnDispose(Action action)
    {
      if (action == null)
        throw new ArgumentNullException("action");
      this.action = action;
    }
    
    public void Dispose()
    {
      Action a = Interlocked.Exchange(ref action, null);
      if (a != null) {
        a();
      }
    }
  }
}