How to set the border color of a particular header cell in DataGridView

Question

Can any one help me to resolve the issue of how to set the border color of a particular header cell in a DataGridView in a C# winform.

I have a DataGridView in C# winform and my requirement is that I want to set the border color of header cell when we click on header cell.

Answer 1

There is no direct way of doing this. You have to draw your own border in CellPainting event handler.

Have a class level variable to store the clicked column header index.

int myClickedColumnHeaderIndex = -1;

Subscribe to below events.

dataGridView1.CellPainting += dataGridView1_CellPainting;
dataGridView1.ColumnHeaderMouseClick += new DataGridViewCellMouseEventHandler(dataGridView1_ColumnHeaderMouseClick);

In ColumnHeaderMouseClick handler store the column index using the class level variable.

void dataGridView1_ColumnHeaderMouseClick(object sender, DataGridViewCellMouseEventArgs e)
{
    if (e.Button == MouseButtons.Left && e.Clicks == 1)
    {
        dataGridView1.InvalidateCell(myClickedColumnHeaderIndex, -1); // this to trigger paint of the old cell inorder to remove the border drawn earlier.
        myClickedColumnHeaderIndex = e.ColumnIndex;
    }
}

In the CellPainting event handler, draw the border using the required color.

void dataGridView1_CellPainting(object sender, DataGridViewCellPaintingEventArgs e)
{
    if (e.RowIndex == -1 && e.ColumnIndex >= 0 && e.ColumnIndex == myClickedColumnHeaderIndex)
    {
        e.Paint(e.CellBounds, DataGridViewPaintParts.All & ~DataGridViewPaintParts.Border);
        using (Pen customPen = new Pen(Color.Blue, 2))
        {
            Rectangle rect = e.CellBounds;
            rect.Width -= 2;
            rect.Height -= 2;
            e.Graphics.DrawRectangle(customPen, rect);
        }
        e.Handled = true;
    }
}

Answer 2

This code draws vertical borde for header cells and data cells for each even column.

private void DgvCalendar_CellPainting(object sender, DataGridViewCellPaintingEventArgs e)
        {
            int columnIndex = 0;

            if (e.RowIndex >= 0 && e.ColumnIndex >= columnIndex)
            {
                if (e.ColumnIndex % 2 == 0)
                {
                    var brush = new SolidBrush(dgvCalendar.ColumnHeadersDefaultCellStyle.BackColor);

                    e.Graphics.FillRectangle(brush, e.CellBounds);

                    brush.Dispose();

                    e.Paint(e.CellBounds, DataGridViewPaintParts.All & ~DataGridViewPaintParts.ContentBackground);

                    ControlPaint.DrawBorder(e.Graphics, e.CellBounds,
                        System.Drawing.Color.Transparent, 1, ButtonBorderStyle.Solid,
                        System.Drawing.Color.Transparent, 1, ButtonBorderStyle.Solid,
                        System.Drawing.Color.CornflowerBlue, 1, ButtonBorderStyle.Solid,
                        System.Drawing.Color.Transparent, 1, ButtonBorderStyle.Solid);

                    e.Handled = true;
                }
            }

            if (e.RowIndex == -1 && e.ColumnIndex >= columnIndex)
            {
                if (e.ColumnIndex % 2 == 0)
                {
                    e.Paint(e.CellBounds, DataGridViewPaintParts.All & ~DataGridViewPaintParts.Border);

                    ControlPaint.DrawBorder(e.Graphics, e.CellBounds,
                          System.Drawing.Color.Transparent, 1, ButtonBorderStyle.Solid,
                          System.Drawing.Color.Transparent, 1, ButtonBorderStyle.Solid,
                          System.Drawing.Color.CornflowerBlue, 1, ButtonBorderStyle.Solid,
                          System.Drawing.Color.Transparent, 1, ButtonBorderStyle.Solid);

                    e.Handled = true;

                    e.Handled = true;
                }
            }
        }