public void And(BitSet set)
{
if (set == null)
throw new ArgumentNullException("set");
int length = Math.Min(_data.Length, set._data.Length);
for (int i = 0; i < length; i++)
_data[i] &= set._data[i];
for (int i = length; i < _data.Length; i++)
_data[i] = 0;
}