SourceGrid.GridVirtual.CheckPositions C# (CSharp) Method

        public virtual void CheckPositions()
        {
            Range complete = CompleteRange;

            if (m_MouseCellPosition.IsEmpty() == false &&
                CompleteRange.Contains(m_MouseCellPosition) == false)
                m_MouseCellPosition = Position.Empty;

            if (m_MouseDownPosition.IsEmpty() == false &&
                CompleteRange.Contains(m_MouseDownPosition) == false)
                m_MouseDownPosition = Position.Empty;

            if (mDragCellPosition.IsEmpty() == false &&
                CompleteRange.Contains(mDragCellPosition) == false)
                mDragCellPosition = Position.Empty;

            //If the selection contains some invalid cells reset the selection state.
            RangeRegion completeRegion = new RangeRegion(complete);
            if (
                (Selection.ActivePosition.IsEmpty() == false && complete.Contains(Selection.ActivePosition) == false) ||
                (Selection.IsEmpty() == false && completeRegion.Contains(Selection.GetSelectionRegion()) == false)
                )
                Selection.ResetSelection(false);
        }