/// <summary>
/// Returns an enumerator that iterates through the collection.
/// </summary>
/// <returns>
/// A <see cref="T:System.Collections.Generic.IEnumerator`1"/> that can be used to iterate through the collection.
/// </returns>
/// <filterpriority>1</filterpriority>
public IEnumerator <TValue> GetEnumerator()
{
List <Guid> deadGuids = new List <Guid>();
foreach (KeyValuePair <Guid, WeakReference <TValue> > kvp in _dictionary)
{
Debug.Assert(kvp.Value != null);
TValue target;
if (!kvp.Value.TryGetTarget(out target))
{
deadGuids.Add(kvp.Key);
}
else
{
yield return(target);
}
}
foreach (Guid guid in deadGuids)
{
WeakReference <TValue> weakReference;
if (!_dictionary.TryRemove(guid, out weakReference) ||
!_parent._observable)
{
continue;
}
ObservableWeakReference <TValue> owf = weakReference as ObservableWeakReference <TValue>;
if (owf != null)
{
owf.Dispose();
}
}
}
/// <summary>
/// Register the finalize event where appropriate.
/// </summary>
/// <param name="key">The key.</param>
/// <param name="weakReference">The weak reference.</param>
private void RegisterFinalize([NotNull] TKey key, [CanBeNull] WeakReference <TValue> weakReference)
{
if (!_observable ||
(weakReference == null))
{
return;
}
ObservableWeakReference <TValue> owf = weakReference as ObservableWeakReference <TValue>;
if (owf == null)
{
return;
}
owf.Finalized += (s, e) =>
{
WeakReference <TValue> oldwr;
if (_dictionary.TryRemove(key, out oldwr) &&
(oldwr != weakReference))
{
// If we removed something else, add it back!
_dictionary.TryAdd(key, oldwr);
}
owf.Dispose();
};
}
/// <summary>
/// Removes the specified value from the group.
/// </summary>
/// <param name="value">The value to remove.</param>
/// <returns>
/// Returns <see langword="true"/> if the value was successfully removed; otherwise returns <see langword="false"/>.
/// </returns>
public bool Remove(TValue value)
{
// Scan dictionary looking for dead elements
List <Guid> deadGuids = new List <Guid>();
bool found = false;
foreach (KeyValuePair <Guid, WeakReference <TValue> > kvp in _dictionary)
{
Debug.Assert(kvp.Value != null);
TValue v;
if (!kvp.Value.TryGetTarget(out v))
{
deadGuids.Add(kvp.Key);
}
if (!_parent._valueComparer.Equals(v, value))
{
continue;
}
deadGuids.Add(kvp.Key);
found = true;
break;
}
foreach (Guid guid in deadGuids)
{
WeakReference <TValue> weakReference;
if (!_dictionary.TryRemove(guid, out weakReference) ||
(weakReference == null))
{
continue;
}
ObservableWeakReference <TValue> owf = weakReference as ObservableWeakReference <TValue>;
if (owf != null)
{
owf.Dispose();
}
}
// If we're down to one remove grouping.
if (_dictionary.Count < 1)
{
WeakGrouping weakGrouping;
_parent._dictionary.TryRemove(Key, out weakGrouping);
}
return(found);
}
/// <summary>
/// Wraps the specified value in a weak reference.
/// </summary>
/// <param name="key">The key.</param>
/// <param name="value">The value.</param>
/// <param name="register">If set to <see langword="true"/> registers the finalize event immediately.</param>
/// <returns>The wrapped value.</returns>
private WeakReference <TValue> Wrap([NotNull] TKey key, [CanBeNull] TValue value, bool register = true)
{
if (value == null)
{
return(null);
}
if (!_observable)
{
return(new WeakReference <TValue>(value, _allowResurrection));
}
ObservableWeakReference <TValue> owf = new ObservableWeakReference <TValue>(value, _allowResurrection);
if (register)
{
RegisterFinalize(key, owf);
}
return(owf);
}
/// <summary>
/// Adds the specified value to the group.
/// </summary>
/// <param name="value">The value to add.</param>
/// <returns>The new <paramref name="value"/> added to the group.</returns>
public WeakGrouping Add([NotNull] TValue value)
{
Guid guid = Guid.NewGuid();
WeakReference <TValue> weakReference;
if (_parent._observable)
{
ObservableWeakReference <TValue> owf = new ObservableWeakReference <TValue>(
value,
_parent._allowResurrection);
owf.Finalized += (s, e) =>
{
WeakReference <TValue> removedValue;
_dictionary.TryRemove(guid, out removedValue);
owf.Dispose();
};
weakReference = owf;
}
else
{
weakReference = new WeakReference <TValue>(value, _parent._allowResurrection);
}
_dictionary.AddOrUpdate(
guid,
g => weakReference,
(g, w) =>
{
if ((_parent._observable) &&
(w != null))
{
ObservableWeakReference <TValue> o =
w as ObservableWeakReference <TValue>;
if (o != null)
{
o.Dispose();
}
}
return(weakReference);
});
return(this);
}
