c# - Custom DataGridView Cell Painting

Question

I'm trying to draw my own grid lines because I want thicker lines than the default data grid view lines. This is the code I'm using to do it:

 private void dgv_Wafer_CellPainting(object sender, DataGridViewCellPaintingEventArgs e)
    {
        using (Pen p = new Pen(Brushes.Black, 12))
        {
            e.Graphics.DrawLine(p, new Point(0, e.CellBounds.Bottom), new Point(e.CellBounds.Right, e.CellBounds.Bottom));
        }
        using (Pen p = new Pen(Brushes.Black, 6))
        {
            e.Graphics.DrawLine(p, new Point(e.CellBounds.Right, 0), new Point(e.CellBounds.Right - 1, e.CellBounds.Bottom));
        }
    }

The lines are drawn but the horizontal lines won't be drawn in the last column and the vertical lines won't be drawn in the last row. The lines are creating a grid that is a column and row too small. Does anyone know how to fix this?

Answer 1

Try setting the e.Handled = true; to control the painting. Add back in the default painting of the cells:

e.PaintBackground(e.ClipBounds, true);
e.PaintContent(e.ClipBounds);
using (Pen p = new Pen(Brushes.Black, 12)) {
  e.Graphics.DrawLine(p, new Point(e.CellBounds.Left, e.CellBounds.Bottom),
                         new Point(e.CellBounds.Right, e.CellBounds.Bottom));
}
using (Pen p = new Pen(Brushes.Black, 6)) {
  e.Graphics.DrawLine(p, new Point(e.CellBounds.Right, e.CellBounds.Top),
                         new Point(e.CellBounds.Right, e.CellBounds.Bottom));
}
e.Handled = true;

Your code was also using 0 for left and top, but the CellBounds values are based on the control's interior space, so you should use e.CellBounds.Left and e.CellBounds.Top

You might want to adjust the points of your line to account for the thickness of those borders, they are bleeding outside of the cell at the moment.