HTML Table 輸出Excel

string html = RenderControl(this.Page);//獲取控制元件最終呈現的HTML,最好是Table
MemoryStream stream = new MemoryStream(Encoding.UTF8.GetBytes(html));
System.IO.MemoryStream ms = stream;
byte[] bt = ms.ToArray();
//客戶端儲存的檔名  
//以字元流的形式下載檔案    
string file = $"output.xls";
System.Web.HttpContext.Current.Response.ContentType = "application/vnd.ms-excel";
System.Web.HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment; filename=" + file);
System.Web.HttpContext.Current.Response.OutputStream.Write(bt, 0, bt.Length);
this.Response.Flush();
this.Response.End();

public static string RenderControl(Control control)
{
    StringWriter stringWriter = new StringWriter(CultureInfo.InvariantCulture);
    HtmlTextWriter htmlTextWriter = new HtmlTextWriter(stringWriter);
    control.RenderControl(htmlTextWriter);
    htmlTextWriter.Flush();
    htmlTextWriter.Close();
    return stringWriter.ToString();
}

<table id="tb" 
    style="border-collapse: collapse; width: 100%; line-height: 30px;border:1px solid black;border-color:#000;width:1200px;" >
    <%--bordercolor="#000000" cellspacing="0" width="300" align="center" bgcolor="#ffffff" border="1"--%>
            <tr>
                <th colspan="<%= dthxry.Rows.Count+8 %>" style="font-size: 20px; height: 60px;border:1px solid black;">
                    <h1><%= sjnf %> 年 <%= jd %> 季度 社群正職/部門正職班子評價得分</h1>
                </th>
            </tr>
            <tr>
                <th rowspan="2" style="<%= css%>">社群
                </th>
                <th rowspan="2" style="<%= css%>">姓名
                </th>
                <th rowspan="2" style="<%= css%>">社群包聯領導
                </th>
                <th rowspan="2" style="<%= css%>">包聯領導評分（40%）
                </th>
                <th colspan="<%= dthxry.Rows.Count+2 %>" style="<%= css%>">班子評分（20%）
                </th>
                <th rowspan="2" style="<%= css%>">線下分（40%）
                </th>
                <th rowspan="2" style="<%= css%>">綜合得分
                </th>
            </tr>
            <tr>
                <%foreach (System.Data.DataRow r in dthxry.Rows)
                    {  %>
                <th style="<%= css%>"><%= r["username"] %></th>
                <%} %>
                <th style="<%= css%>">班子總分</th>
                <th style="<%= css%>">班子平均分（20%）</th>
            </tr>
            <tbody>

                <% foreach (System.Data.DataRow r in dtData.Rows)
                    {  %>
                <tr>
                    <th style="<%= css%>"><%=r["deptname"] %></th>
                    <th style="<%= css%>"><%=r["username"] %></th>
                    <th style="<%= css%>">社群包聯領導</th>
                    <th style="<%= css%>"><%=r["blldpf"] %></th>
                    <% foreach (string s in cols)
                        {  %>
                    <th style="<%= css%>"><%=r[s] %></th>
                    <%} %>
                    <th style="<%= css%>"><%= ((decimal)r["bzzf"]).ToString("0.##") %></th>
                    <th style="<%= css%>"><%=((decimal)r["bzpjf"]).ToString("0.##") %></th>
                    <th style="<%= css%>"><%=((decimal)r["xxf"]).ToString("0.##") %></th>
                    <th style="<%= css%>"><%=((decimal)r["zhdf"]).ToString("0.##") %></th>
                </tr>
                <%} %>
            </tbody>
</table>