public void Undo()
{
if (!Executed)
{
throw new CommandNotExecutedException();
}
if (!_Db.RemoveLink(_ParentNode, _ChildNode))
{
throw new CommandFailedDbWriteException();
}
_ParentNode.RemoveChild(_ChildNode);
_ChildNode.RemoveParent(_ParentNode);
Executed = false;
}
public void Execute()
{
if (Executed)
{
throw new CommandAlreadyExecutedException();
}
if (!_Db.RemoveLink(_ParentNode, _ChildNode))
{
throw new CommandFailedDbWriteException();
}
_ParentNode.RemoveChild(_ChildNode);
_ChildNode.RemoveParent(_ParentNode);
Executed = true;
}