/// <summary>
    /// this function checks if the user hit the expand (+) or collapse (-) icon.
    /// if it was hit it will return true
    /// </summary>
    /// <param name="e">mouse click event arguments</param>
    /// <returns>returns true if the icon was hit, false otherwise</returns>
    internal bool IsIconHit(DataGridViewCellMouseEventArgs e)
    {
        if (e.ColumnIndex < 0)
        {
            return(false);
        }

        OutlookGrid grid      = (OutlookGrid)this.DataGridView;
        Rectangle   rowBounds = grid.GetRowDisplayRectangle(this.Index, false);
        int         x         = e.X;

        DataGridViewColumn c = grid.Columns[e.ColumnIndex];

        if (this.isGroupRow &&
            (c.DisplayIndex == 0) &&
            (x > rowBounds.Left + 4) &&
            (x < rowBounds.Left + 16) &&
            (e.Y > rowBounds.Height - 18) &&
            (e.Y < rowBounds.Height - 7))
        {
            return(true);
        }

        return(false);


        //System.Diagnostics.Debug.WriteLine(e.ColumnIndex);
    }
    /// <summary>
    /// the main difference with a Group row and a regular row is the way it is painted on the control.
    /// the Paint method is therefore overridden and specifies how the Group row is painted.
    /// Note: this method is not implemented optimally. It is merely used for demonstration purposes
    /// </summary>
    /// <param name="graphics"></param>
    /// <param name="clipBounds"></param>
    /// <param name="rowBounds"></param>
    /// <param name="rowIndex"></param>
    /// <param name="rowState"></param>
    /// <param name="isFirstDisplayedRow"></param>
    /// <param name="isLastVisibleRow"></param>
    protected override void Paint(System.Drawing.Graphics graphics, System.Drawing.Rectangle clipBounds, System.Drawing.Rectangle rowBounds, int rowIndex, DataGridViewElementStates rowState, bool isFirstDisplayedRow, bool isLastVisibleRow)
    {
        if (this.isGroupRow)
        {
            OutlookGrid grid            = (OutlookGrid)this.DataGridView;
            int         rowHeadersWidth = grid.RowHeadersVisible ? grid.RowHeadersWidth : 0;

            // this can be optimized
            Brush brush  = new SolidBrush(grid.DefaultCellStyle.BackColor);
            Brush brush2 = new SolidBrush(Color.FromKnownColor(KnownColor.GradientActiveCaption));

            int       gridwidth  = grid.Columns.GetColumnsWidth(DataGridViewElementStates.Displayed);
            Rectangle rowBounds2 = grid.GetRowDisplayRectangle(this.Index, true);

            // draw the background
            graphics.FillRectangle(brush, rowBounds.Left + rowHeadersWidth - grid.HorizontalScrollingOffset, rowBounds.Top, gridwidth, rowBounds.Height - 1);

            // draw text, using the current grid font
            graphics.DrawString(group.Text, grid.Font, Brushes.Black, rowHeadersWidth - grid.HorizontalScrollingOffset + 23, rowBounds.Bottom - 18);

            //draw bottom line
            graphics.FillRectangle(brush2, rowBounds.Left + rowHeadersWidth - grid.HorizontalScrollingOffset, rowBounds.Bottom - 2, gridwidth - 1, 2);

            // draw right vertical bar
            if (grid.CellBorderStyle == DataGridViewCellBorderStyle.SingleVertical || grid.CellBorderStyle == DataGridViewCellBorderStyle.Single)
            {
                graphics.FillRectangle(brush2, rowBounds.Left + rowHeadersWidth - grid.HorizontalScrollingOffset + gridwidth - 1, rowBounds.Top, 1, rowBounds.Height);
            }

            if (group.Collapsed)
            {
                if (grid.ExpandIcon != null)
                {
                    graphics.DrawImage(grid.ExpandIcon, rowBounds.Left + rowHeadersWidth - grid.HorizontalScrollingOffset + 4, rowBounds.Bottom - 18, 11, 11);
                }
            }
            else
            {
                if (grid.CollapseIcon != null)
                {
                    graphics.DrawImage(grid.CollapseIcon, rowBounds.Left + rowHeadersWidth - grid.HorizontalScrollingOffset + 4, rowBounds.Bottom - 18, 11, 11);
                }
            }
            brush.Dispose();
            brush2.Dispose();
        }
        base.Paint(graphics, clipBounds, rowBounds, rowIndex, rowState, isFirstDisplayedRow, isLastVisibleRow);
    }