How to change the border color of some cells in DataGridView?

datagridview, winforms

Solution

You can draw a rectangle. In this example I put a red boder on the selected cells.

private void dataGridView_CellPainting(object sender, DataGridViewCellPaintingEventArgs e)
{
    if (e.RowIndex >= 0 && e.ColumnIndex >= 0)
    {
        if (dataGridView.Rows[e.RowIndex].Cells[e.ColumnIndex].Selected == true)
        {
            e.Paint(e.CellBounds, DataGridViewPaintParts.All & ~DataGridViewPaintParts.Border);
            using (Pen p = new Pen(Color.Red, 1))
            {
                Rectangle rect = e.CellBounds;
                rect.Width -= 2;
                rect.Height -= 2;
                e.Graphics.DrawRectangle(p, rect);
            }
            e.Handled = true;
        }
    }
}

Problem

Original source