private void Insert(int index, Object key, Object value)
{
if (_size == _keys.Length) EnsureCapacity(_size + 1);
if (index < _size)
{
Array.Copy(_keys, index, _keys, index + 1, _size - index);
Array.Copy(_values, index, _values, index + 1, _size - index);
}
_keys[index] = key;
_values[index] = value;
_size++;
_version++;
}