protected void Handle(ILine _object)
        {
            if (firstLine == null && _object is INodeLine)
            {
                firstLine = _object as INodeLine;
                if (_object is ISelectable)
                    ((ISelectable)_object).IsSelected = true;
            }

            else if (firstLine != null && secondLine == null )
            {
                secondLine = _object ;
                if ( _object is ISelectable )
                ((ISelectable)secondLine).IsSelected = true;

                Modification();

                Clear();
            }
        }
 public SplitCommand(INodeLine line)
 {
     this.line = line;
 }
        protected void Clear()
        {
            if (firstLine is ISelectable )
                ((ISelectable)firstLine).IsSelected = false;
            if (secondLine is ISelectable)
                ((ISelectable)secondLine).IsSelected = false;

            firstLine = null;
            secondLine = null;
        }