protected override bool RemoveItem(TKey key)
{
LinkedKeyValuePair l;
if (Backend.TryGetValue(key, out l))
{
if (l != null)
{
LinkedKeyValuePair pre = l.Previous;
LinkedKeyValuePair nxt = l.Next;
if (pre != null)
{
pre.Next = nxt;
}
else
{
First = nxt;
}
if (nxt != null)
{
nxt.Previous = pre;
}
else
{
Last = pre;
}
}
return(Backend.Remove(key));
}
return(false);
}
public void Clear()
{
Updates++;
Backend.Clear();
First = null;
Last = null;
}
public LinkedDictionaryEnumerator(AbstractLinkedDictionary <TKey, TValue> parent, bool forward)
{
_parent = parent;
_forward = forward;
_current = null;
_updates = parent.Updates;
}
protected override void SetItem(TKey key, TValue value)
{
LinkedKeyValuePair l = GetItem(key);
if (l != null)
{
RemoveItem(key);
}
AddItem(key, value);
}
public bool MoveNext()
{
if (_parent.Updates != _updates)
{
throw new InvalidOperationException("Collection was modified after the enumerator was created");
}
if (_current == null)
{
_current = _forward ? _parent.First : _parent.Last;
}
else
{
_current = _forward ? _current.Next : _current.Previous;
}
return(_current != null);
}
protected override LinkedKeyValuePair GetItem(TKey key)
{
LinkedKeyValuePair l;
if (!Backend.TryGetValue(key, out l))
{
return(null);
}
if (l == null)
{
return(null);
}
LinkedKeyValuePair nxt = l.Next;
if (nxt != null) // last => no-change
{
Updates++; // looking is updating
// note, atleast 2 items in chain now, since l != last
LinkedKeyValuePair pre = l.Previous;
if (pre == null)
{
First = nxt;
}
else
{
pre.Next = l.Next;
}
nxt.Previous = pre; // nxt != null since l != last
Last.Next = l;
l.Next = null;
l.Previous = Last;
Last = l;
}
return(l);
}
protected override void AddItem(TKey key, TValue value)
{
if (Backend.ContainsKey(key))
{
throw new ArgumentException($"Key \"{key}\" already present in dictionary");
}
var l = new LinkedKeyValuePair(key, value, Last, null);
if (Last != null)
{
Last.Next = l;
}
Last = l;
if (First == null)
{
First = l;
}
Backend.Add(key, l);
}
public void Reset()
{
_current = null;
}
public LinkedKeyValuePair(TKey key, TValue value, LinkedKeyValuePair prev, LinkedKeyValuePair next)
{
KeyValuePair = new KeyValuePair <TKey, TValue>(key, value);
Previous = prev;
Next = next;
}
