Merge RTL Datagridview columns header in C#

Question

I want to merge 3 Datagridview columns headers (the 3rd, 4th, and the 5th

columns) and the RightToleft property of the Datagridview is enabled. i user

this code:

private void PromotionButton_Click(object sender, EventArgs e)
    {
        dataGridView1.ColumnHeadersHeight = dataGridView1.ColumnHeadersHeight * 2;
        dataGridView1.ColumnHeadersDefaultCellStyle.Alignment = DataGridViewContentAlignment.MiddleCenter;
        dataGridView1.CellPainting += new DataGridViewCellPaintingEventHandler(dataGridView1_CellPainting);
        dataGridView1.Paint += new PaintEventHandler(dataGridView1_Paint);
        dataGridView1.Scroll += new ScrollEventHandler(dataGridView1_Scroll);
        dataGridView1.ColumnWidthChanged += new DataGridViewColumnEventHandler(dataGridView1_ColumnWidthChanged);

    }
private void dataGridView1_Paint(object sender, PaintEventArgs e)
    {
        for (int j = 2; j < 5; j++)
        {
            Rectangle r1 = dataGridView1.GetCellDisplayRectangle(j, -1, true);
            int w2 = dataGridView1.GetCellDisplayRectangle(j + 1, -1, true).Width;
            r1.X += 1;
            r1.Y += 1;
            r1.Width = r1.Width + w2 - 2;
            r1.Height = r1.Height / 2 - 2;
            e.Graphics.FillRectangle(new SolidBrush(dataGridView1.ColumnHeadersDefaultCellStyle.BackColor), r1);

            StringFormat format = new StringFormat();

            format.Alignment = StringAlignment.Center;
            format.LineAlignment = StringAlignment.Center;
            e.Graphics.DrawString("رياضيات", dataGridView1.ColumnHeadersDefaultCellStyle.Font,
                new SolidBrush(dataGridView1.ColumnHeadersDefaultCellStyle.ForeColor), r1, format);
        }
void dataGridView1_ColumnWidthChanged(object sender, DataGridViewColumnEventArgs e)
    {
        Rectangle rtHeader = dataGridView1.DisplayRectangle;
        rtHeader.Height = dataGridView1.ColumnHeadersHeight / 2;
        dataGridView1.Invalidate(rtHeader);
    }
    void dataGridView1_Scroll(object sender, ScrollEventArgs e)
    {
        Rectangle rtHeader = dataGridView1.DisplayRectangle;
        rtHeader.Height = dataGridView1.ColumnHeadersHeight / 2;
        dataGridView1.Invalidate(rtHeader);

    }

    void dataGridView1_CellPainting(object sender, DataGridViewCellPaintingEventArgs e)
    {
        if (e.RowIndex == -1 && e.ColumnIndex > -1)
        {
            Rectangle r2 = e.CellBounds;
            r2.Y += e.CellBounds.Height / 2;
            r2.Height = e.CellBounds.Height / 2;
            e.PaintBackground(r2, true);
            e.PaintContent(r2);
            e.Handled = true;
        }

    }

But the result was not like what i want, it was like this:

So how to solve this?

Answer 1

Assuming you want those three columns merged with only one print of the merge text, and you want to merge columns indexed 2-4:

1. Remove the loop.
2. Get the width of all three desired columns (instead of column j and j+1 )
3. Start your Rectangle at the left-most column (column 4, not 2) since your grid has RightToLeft enabled.

private void dataGridView1_Paint(object sender, PaintEventArgs e)
{
    Rectangle r1 = dataGridView1.GetCellDisplayRectangle(4, -1, true);
    int w2 = dataGridView1.GetCellDisplayRectangle(3, -1, true).Width;
    int w3 = dataGridView1.GetCellDisplayRectangle(2, -1, true).Width;
    r1.X += 1;
    r1.Y += 1;
    r1.Width = r1.Width + w2 + w3;
    r1.Height = r1.Height / 2 - 2;
    e.Graphics.FillRectangle(new SolidBrush(dataGridView1.ColumnHeadersDefaultCellStyle.BackColor), r1);

    StringFormat format = new StringFormat();

    format.Alignment = StringAlignment.Center;
    format.LineAlignment = StringAlignment.Center;
    e.Graphics.DrawString("رياضيات", dataGridView1.ColumnHeadersDefaultCellStyle.Font,
        new SolidBrush(dataGridView1.ColumnHeadersDefaultCellStyle.ForeColor), r1, format);
}

Also, I would suggest using the following alignment to prevent your header text from partial obstruction:

dataGridView1.ColumnHeadersDefaultCellStyle.Alignment = DataGridViewContentAlignment.BottomCenter;