System.Data.SQLite

    /// <summary>
    /// Used internally to keep track of memory allocated for aggregate functions
    /// </summary>
    private IntPtr                     _interopCookie;
    /// <summary>
    /// Internal array used to keep track of aggregate function context data
    /// </summary>
    private Dictionary<long, object> _contextDataList;

    /// <summary>
    /// Holds a reference to the callback function for user functions
    /// </summary>
    private SQLiteCallback  _InvokeFunc;
    /// <summary>
    /// Holds a reference to the callbakc function for stepping in an aggregate function

    private static List<SQLiteFunctionAttribute> _registeredFunctions = new List<SQLiteFunctionAttribute>();

    /// <summary>
    /// Internal constructor, initializes the function's internal variables.
    /// </summary>
    protected SQLiteFunction()
    {
      _contextDataList = new Dictionary<long, object>();
    }

    /// <summary>
    /// Returns a reference to the underlying connection's SQLiteConvert class, which can be used to convert
    /// strings and DateTime's into the current connection's encoding schema.
    /// </summary>
    public SQLiteConvert SQLiteConvert

    /// </remarks>
    /// <param name="context">A raw context pointer</param>
    /// <param name="nArgs">Number of arguments passed in</param>
    /// <param name="argsptr">A pointer to the array of arguments</param>
    internal void StepCallback(IntPtr context, int nArgs, IntPtr argsptr)
    {
      int n = _base.AggregateCount(context);
      long nAux;
      object obj = null;

      nAux = (long)_base.AggregateContext(context);
      if (n > 1) obj = _contextDataList[nAux];

      Step(ConvertParams(nArgs, argsptr), n, ref obj);
      _contextDataList[nAux] = obj;      
    }

    /// <summary>
    /// An internal aggregate Final function callback, which wraps the context pointer and calls the virtual Final() method.
    /// </summary>
    /// <param name="context">A raw context pointer</param>
    /// <param name="nArgs">Not used, always zero</param>
    /// <param name="argsptr">Not used, always zero</param>
    internal void FinalCallback(IntPtr context, int nArgs, IntPtr argsptr)
    {
      long n = (long)_base.AggregateContext(context);
      object obj = null;

      if (_contextDataList.ContainsKey(n))
      {
        obj = _contextDataList[n];
        _contextDataList.Remove(n);
      }

    /// </summary>
    public void Dispose()
    {
      Dispose(true);

      IDisposable disp;

      foreach (KeyValuePair<long, object> kv in _contextDataList)
      {
        disp = kv.Value as IDisposable;
        if (disp != null)
          disp.Dispose();
      }
      _contextDataList.Clear();