<asp:Label ID="lb_show" runat="server" 
            style="position:absolute; top: 196px; left: 88px; height: 16px; word-break:break-all"/></asp:Label>

    protected void btn_submit_Click(object sender, EventArgs e)
    {
        string message = string.Empty;
        try
        {
            int min = Convert.ToInt32(txt_start.Text);
            int max = Convert.ToInt32(txt_end.Text);
            for (int i = min; i <= max; i++)
            {
                for (int j = min; j <= i; j++)
                {
                    message += string.Format("{0}*{1}={2} ", j, i, i * j);
                }
                message += "\r\n";
            }
        }
        catch
        {
            message = "请输入正确数字";
        }
        lb_show.Text = message;
    }