private DataSet ds = new DataSet();
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                ds.Tables.Add();
                ds.Tables[0].Columns.Add("a", typeof(string)); 
                ds.Tables[0].Columns.Add("b", typeof(string));
                ds.Tables[0].Columns.Add("c", typeof(string));
            }
        }

        protected void Button1_Click(object sender, ImageClickEventArgs e)
        {
            DataRow dr = ds.Tables[0].NewRow();
            dr[0] = txtBrand.Text;
            dr[1] = txtName.Text;
            dr[2] = txtType.Text;
            ds.Tables[0].Rows.Add(dr);
        }