problem while exporting to excel

namespace Sqltoexcel
{
    public partial class _Default : System.Web.UI.Page
    {
        SqlConnection conn = new SqlConnection("Data Source=ARKA-PC;Initial Catalog=rgdb;User Id = sa;;password = 12345");
        DataTable dt = new DataTable();
        
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void btn1_Click(object sender, EventArgs e)
        {
            string str = "select * from reg_table";
            SqlDataAdapter sda = new SqlDataAdapter(str, conn);
            sda.Fill(dt);
            exporttosql(dt);
        }

        public void exporttosql(DataTable dt)
        {
            HttpContext context = HttpContext.Current;
            string attach = "attachment;filename = example.xls";
            context.Response.ClearContent();
            context.Response.AddHeader("content-disposition",attach);
            context.Response.ContentType = "application/ms-excel";
            string sep = "";

            if (dt != null)
            { 
                foreach(DataColumn dc in dt.Columns)
                {
                    context.Response.Write(sep + dc.ColumnName);
                    sep = "\t";
                }
                context.Response.Write(System.Environment.NewLine);

                foreach(DataRow dr in dt.Rows)
                {
                    sep = "";
                    for (int i = 0; i < dt.Columns.Count;i++)
                    {
                        context.Response.Write(sep + "\"" + dr.ToString() + "\"");
                        sep = "\t";
                    }
                    context.Response.Write(System.Environment.NewLine); 
                }
                context.Response.End();
            }
            //lbl1.Text = "Data Transfered";
            //lbl1.Visible = true;             
        }
    }
}

The above code is used to export data from sql to excel. The data is exported but i am not getting the desired value. I am providing a screen shot attached of the excel sheet.
Please help me in this....

Thanks and Regards
Akiii