margin header cell ใน datagridview c# มีวิธีเขียนโค้ดยังไงครับ

namespace Sample5
{
    public partial class DgvColumnHeaderMerge : Form
    {
        public DgvColumnHeaderMerge()
        {
            InitializeComponent();
        }
 
        private void DgvColumnHeaderMerge_Load(object sender, EventArgs e)
        {
            this.dataGridView1.Columns.Add("JanWin", "Win");
            this.dataGridView1.Columns.Add("JanLoss", "Loss");
            this.dataGridView1.Columns.Add("FebWin", "Win");
            this.dataGridView1.Columns.Add("FebLoss", "Loss");
            this.dataGridView1.Columns.Add("MarWin", "Win");
            this.dataGridView1.Columns.Add("MarLoss", "Loss");
            this.dataGridView1.Columns.Add("AprWin", "Win");
            this.dataGridView1.Columns.Add("AprLoss", "Loss");
            this.dataGridView1.Columns.Add("MayWin", "Win");
            this.dataGridView1.Columns.Add("MayLoss", "Loss");
 
            for (int j = 0; j < this.dataGridView1.ColumnCount; j++)
            {
                this.dataGridView1.Columns[j].Width = 45;
            }
            this.dataGridView1.ColumnHeadersHeightSizeMode = DataGridViewColumnHeadersHeightSizeMode.EnableResizing;
            this.dataGridView1.ColumnHeadersHeight = this.dataGridView1.ColumnHeadersHeight * 2;
            this.dataGridView1.ColumnHeadersDefaultCellStyle.Alignment = DataGridViewContentAlignment.BottomCenter;
            this.dataGridView1.CellPainting += new DataGridViewCellPaintingEventHandler(dataGridView1_CellPainting);
            this.dataGridView1.Paint += new PaintEventHandler(dataGridView1_Paint);
 
            this.dataGridView1.Scroll += new ScrollEventHandler(dataGridView1_Scroll);
            this.dataGridView1.ColumnWidthChanged += new DataGridViewColumnEventHandler(dataGridView1_ColumnWidthChanged);
        }
 
        void dataGridView1_ColumnWidthChanged(object sender, DataGridViewColumnEventArgs e)
        {
            Rectangle rtHeader = this.dataGridView1.DisplayRectangle;
            rtHeader.Height = this.dataGridView1.ColumnHeadersHeight / 2;
            this.dataGridView1.Invalidate(rtHeader);
        }
 
        void dataGridView1_Scroll(object sender, ScrollEventArgs e)
        {
            Rectangle rtHeader = this.dataGridView1.DisplayRectangle;
            rtHeader.Height = this.dataGridView1.ColumnHeadersHeight / 2;
            this.dataGridView1.Invalidate(rtHeader);
        }
 
        void dataGridView1_Paint(object sender, PaintEventArgs e)
        {
            string[] monthes = { "January", "February", "March","April" ,"May"};
            for (int j = 0; j < 10;)
            {
                Rectangle r1 = this.dataGridView1.GetCellDisplayRectangle(j, -1,true);
                int w2 = this.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(this.dataGridView1.ColumnHeadersDefaultCellStyle.BackColor), r1);
                StringFormat format = new StringFormat();
                format.Alignment = StringAlignment.Center;
                format.LineAlignment = StringAlignment.Center;
                e.Graphics.DrawString(monthes[j/2],
                    this.dataGridView1.ColumnHeadersDefaultCellStyle.Font,
                    new SolidBrush(this.dataGridView1.ColumnHeadersDefaultCellStyle.ForeColor),
                    r1,
                    format);
                j += 2;
            }
        }
 
        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;
            }
        }
    }
}
 

Public Partial Class DgvColumnHeaderMerge
		Inherits Form
		Public Sub New()
			InitializeComponent()
		End Sub

		Private Sub DgvColumnHeaderMerge_Load(sender As Object, e As EventArgs)
			Me.dataGridView1.Columns.Add("JanWin", "Win")
			Me.dataGridView1.Columns.Add("JanLoss", "Loss")
			Me.dataGridView1.Columns.Add("FebWin", "Win")
			Me.dataGridView1.Columns.Add("FebLoss", "Loss")
			Me.dataGridView1.Columns.Add("MarWin", "Win")
			Me.dataGridView1.Columns.Add("MarLoss", "Loss")
			Me.dataGridView1.Columns.Add("AprWin", "Win")
			Me.dataGridView1.Columns.Add("AprLoss", "Loss")
			Me.dataGridView1.Columns.Add("MayWin", "Win")
			Me.dataGridView1.Columns.Add("MayLoss", "Loss")

			For j As Integer = 0 To Me.dataGridView1.ColumnCount - 1
				Me.dataGridView1.Columns(j).Width = 45
			Next
			Me.dataGridView1.ColumnHeadersHeightSizeMode = DataGridViewColumnHeadersHeightSizeMode.EnableResizing
			Me.dataGridView1.ColumnHeadersHeight = Me.dataGridView1.ColumnHeadersHeight * 2
			Me.dataGridView1.ColumnHeadersDefaultCellStyle.Alignment = DataGridViewContentAlignment.BottomCenter
			Me.dataGridView1.CellPainting += New DataGridViewCellPaintingEventHandler(AddressOf dataGridView1_CellPainting)
			Me.dataGridView1.Paint += New PaintEventHandler(AddressOf dataGridView1_Paint)

			Me.dataGridView1.Scroll += New ScrollEventHandler(AddressOf dataGridView1_Scroll)
			Me.dataGridView1.ColumnWidthChanged += New DataGridViewColumnEventHandler(AddressOf dataGridView1_ColumnWidthChanged)
		End Sub

		Private Sub dataGridView1_ColumnWidthChanged(sender As Object, e As DataGridViewColumnEventArgs)
			Dim rtHeader As Rectangle = Me.dataGridView1.DisplayRectangle
			rtHeader.Height = Me.dataGridView1.ColumnHeadersHeight / 2
			Me.dataGridView1.Invalidate(rtHeader)
		End Sub

		Private Sub dataGridView1_Scroll(sender As Object, e As ScrollEventArgs)
			Dim rtHeader As Rectangle = Me.dataGridView1.DisplayRectangle
			rtHeader.Height = Me.dataGridView1.ColumnHeadersHeight / 2
			Me.dataGridView1.Invalidate(rtHeader)
		End Sub

		Private Sub dataGridView1_Paint(sender As Object, e As PaintEventArgs)
			Dim monthes As String() = {"January", "February", "March", "April", "May"}
			Dim j As Integer = 0
			While j < 10
				Dim r1 As Rectangle = Me.dataGridView1.GetCellDisplayRectangle(j, -1, True)
				Dim w2 As Integer = Me.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(Me.dataGridView1.ColumnHeadersDefaultCellStyle.BackColor), r1)
				Dim format As New StringFormat()
				format.Alignment = StringAlignment.Center
				format.LineAlignment = StringAlignment.Center
				e.Graphics.DrawString(monthes(j / 2), Me.dataGridView1.ColumnHeadersDefaultCellStyle.Font, New SolidBrush(Me.dataGridView1.ColumnHeadersDefaultCellStyle.ForeColor), r1, format)
				j += 2
			End While
		End Sub

		Private Sub dataGridView1_CellPainting(sender As Object, e As DataGridViewCellPaintingEventArgs)
			If e.RowIndex = -1 AndAlso e.ColumnIndex > -1 Then
				Dim r2 As Rectangle = e.CellBounds
				r2.Y += e.CellBounds.Height / 2
				r2.Height = e.CellBounds.Height / 2

				e.PaintBackground(r2, True)

				e.PaintContent(r2)
				e.Handled = True
			End If
		End Sub
	End Class
End Namespace