procedure RefreshWriters(AWriters: TDictionary<TSharedHandle, TWriterNotify>);
var
  LWriter: TSharedHandle;
  Li: Integer;
begin
    for LWriter in AWriters.Keys do
      AWriters[LWriter] := wnUnregister;

    for Li := 0 to GetWriterCount - 1 do begin
      LWriter := GetWriterHandle(Li);
      if AWriters.ContainsKey(LWriter) then
        AWriters[LWriter] := wnNothing
      else
        AWriters.Add(LWriter, wnRegister);
    end;
end;

  TDictionary<TKey,TValue> = class(TEnumerable<TPair<TKey,TValue>>)
  private type
    TItem = record
      HashCode: Integer;
      Key: TKey;
      Value: TValue;
    end;
    TItemArray = array of TItem;
  private
    FItems: TItemArray;
    FCount: Integer;
    function GetBucketIndex(const Key: TKey; HashCode: Integer): Integer;
    function Hash(const Key: TKey): Integer;
..........
function TDictionary<TKey,TValue>.ContainsKey(const Key: TKey): Boolean;
begin
  Result := GetBucketIndex(Key, Hash(Key)) >= 0;
end;

function TDictionary<TKey,TValue>.TryGetValue(const Key: TKey; out Value: TValue): Boolean;
var
  index: Integer;
begin
  index := GetBucketIndex(Key, Hash(Key));
  Result := index >= 0;
  if Result then
    Value := FItems[index].Value
  else
    Value := Default(TValue);
end;

      TValueEnumerator = class(TEnumerator<TValue>)
      private
        FDictionary: TDictionary<TKey,TValue>;
        FIndex: Integer;
        function GetCurrent: TValue;
      protected
        function DoGetCurrent: TValue; override;
        function DoMoveNext: Boolean; override;
      public
        constructor Create(const ADictionary: TDictionary<TKey,TValue>);
        property Current: TValue read GetCurrent;
        function MoveNext: Boolean;
      end;