Programmatically get data from GridView using C# in ASP.NET

        protected void Page_Load(object sender, EventArgs e)
        {
            StringBuilder strB = new StringBuilder();

            strB.Append("<table border=1>");

            for (int k = 0; k< dg.Rows.Count;k++)
            {
                strB.AppendLine("<tr>");
                if (k== 0)
                {
                    for (int j = 0; j < dg.Columns.Count; j++)
                    {
                        strB.AppendLine("<td align='center' valign='middle'>" +
                                        dg.Columns[j].ToString() + "</td>"); //Here i'm getting Header text value instead of cell value
                    }
                }
                else
                {
                    for (int j = 0; j < dg.Columns.Count; j++)
                    {
                        strB.AppendLine("<td align='center' valign='middle'>" + dg.Rows[i].Cells[j].Text
                                         + "</td>"); 
                    }
                }
                strB.AppendLine("</tr>");

            }
            

            strB.Append("</table>");
            this.Page.Form.InnerHtml=strB.ToString();
        }