Control1.Attributes.Add("","");

protected void Page_Load(object sender, EventArgs e)
{
        DataTable dt = new DataTable();
        dt.Columns.Add("Name");
        dt.Columns.Add("City");
        DataRow dr;
        for (int i = 0; i < 5; i++)
        {
            dr = dt.NewRow();
            dr[0] = "Name " + (i + 1);
            dr[1] = "City " + (i + 1);
            dt.Rows.Add(dr);
        }
        grd.DataSource = dt;
        grd.DataBind();
}

protected void OnDataBound(object sender, GridViewRowEventArgs e)
{
        string STR = e.Row.Cells[0].Text;

        TableCell TC = new TableCell();
        e.Row.Cells.Add(TC);
        TC = new TableCell();
        e.Row.Cells.Add(TC);
        
        if (e.Row.RowType == DataControlRowType.Header)
        {
            e.Row.Cells[2].Text = "Text Box";
            e.Row.Cells[3].Text = "DropDownList";
        }
        else
        {
            TextBox txt = new TextBox();
            txt.ID = "TEST";
            e.Row.Cells[2].Controls.Add(txt);
            
            DropDownList ddl = new DropDownList();
            ddl.ID = "ddl";
            e.Row.Cells[3].Controls.Add(ddl);
        }
}