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//
// System.WeakReference.cs
//
// Author:
// Ajay kumar Dwivedi (adwiv@yahoo.com)
//
//
// Copyright (C) 2004 Novell, Inc (http://www.novell.com)
//
// 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.Runtime.Serialization;
using System.Runtime.InteropServices;
namespace System
{
[Serializable]
[ComVisible (true)]
public class WeakReference : ISerializable
{
//Fields
private bool isLongReference;
private GCHandle gcHandle;
// Helper method for constructors
//Should not be called from any other method.
private void AllocateHandle (Object target)
{
if (isLongReference) {
gcHandle = GCHandle.Alloc (target, GCHandleType.WeakTrackResurrection);
}
else {
gcHandle = GCHandle.Alloc (target, GCHandleType.Weak);
}
}
//Constructors
#if MOBILE
protected WeakReference ()
{
}
#endif
public WeakReference (object target)
: this (target, false)
{
}
public WeakReference (object target, bool trackResurrection)
{
isLongReference = trackResurrection;
AllocateHandle (target);
}
protected WeakReference (SerializationInfo info, StreamingContext context)
{
if (info == null)
throw new ArgumentNullException ("info");
isLongReference = info.GetBoolean ("TrackResurrection");
Object target = info.GetValue ("TrackedObject", typeof (System.Object));
AllocateHandle (target);
}
// Properties
public virtual bool IsAlive {
get {
//Target property takes care of the exception
return (Target != null);
}
}
public virtual object Target {
get {
// This shouldn't throw an exception after finalization
// http://blogs.msdn.com/b/yunjin/archive/2005/08/31/458231.aspx
if (!gcHandle.IsAllocated)
return null;
return gcHandle.Target;
}
set
{
gcHandle.Target = value;
}
}
public virtual bool TrackResurrection {
get {
return isLongReference;
}
}
//Methods
~WeakReference ()
{
gcHandle.Free ();
}
public virtual void GetObjectData (SerializationInfo info, StreamingContext context)
{
if (info == null)
throw new ArgumentNullException ("info");
info.AddValue ("TrackResurrection", TrackResurrection);
try {
info.AddValue ("TrackedObject", Target);
} catch (Exception) {
info.AddValue ("TrackedObject", null);
}
}
}
}
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