asp.net后台导出excel的方法：使用System.Web.HttpContext.Current.Response导出excel

protected void ToExcel(DataTable dt, string FileName)
{
StringBuilder sb = new StringBuilder();
sb.Append("<style type=\"text/css\">");
sb.Append("<!--");
sb.Append(".text");
sb.Append("{mso-style-parent:style0;");
sb.Append("font-size:10.0pt;");
sb.Append("font-family:\"Arial Unicode MS\", sans-serif;");
sb.Append("mso-font-charset:0;");
sb.Append(@"mso-number-format:\@;");
sb.Append("text-align:center;");
sb.Append("border:.5pt solid black;");
sb.Append("white-space:normal;}");
sb.Append("-->");
sb.Append("</style>");
sb.Append("<table cellspacing=\"0\" rules=\"all\" border=\"1\" style=\"border-collapse:collapse;\">");

DataRow[] myRow = dt.Select();
int i = 0;
int cl = dt.Columns.Count;

//定义标题
sb.Append("<tr align=\"Center\" style=\"font-weight:bold;\">");
sb.Append("<td colspan=\"" + cl + "\" style =\" height : 25px; font-size: 20pt;\">"+ DropEnterprise.SelectedItem + "</td>");
sb.Append("</tr>");

//定义中间标题
sb.Append("<tr align=\"Center\" style=\"font-weight:bold;\">");
sb.Append("<td >" + txtStart.Text + "</td>");
for (i = 0; i < cl - 2; i++)
{
sb.Append("<td ></td>");
}
sb.Append("<td >" + DropEnterprise.SelectedItem + "</td>");
sb.Append("</tr>");

//定义字段名
sb.Append("<tr align=\"Center\" style=\"font-weight:bold;\">");
for (i = 0; i < cl; i++)
{
if (i == (cl - 1))
{
sb.Append("<td>" + dt.Columns[i].ColumnName.ToString() + "</td></tr>");
}
else
{
//ls_item += dt.Columns[i].ColumnName.ToString() + "\t";
sb.Append("<td>" + dt.Columns[i].ColumnName.ToString() + "</td>");
}
}

//定义数据
foreach (DataRow row in myRow)
{
sb.Append("<tr align=\"Center\">");
for (i = 0; i < cl; i++)
{
if (i == (cl - 1))
{
sb.Append("<td>" + row[i].ToString() + "</td></tr>");
}
else
{
//ls_item += dt.Columns[i].ColumnName.ToString() + "\t";
sb.Append("<td>" + row[i].ToString() + "</td>");
}
}

}
sb.Append("</table>");

System.Web.HttpContext.Current.Response.Clear();
System.Web.HttpContext.Current.Response.Charset = "GB2312";
// System.Web.HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.UTF8;
// 添加头信息，为"文件下载/另存为"对话框指定默认文件名
System.Web.HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment; filename=" +  System.Web.HttpUtility.UrlEncode(FileName, System.Text.Encoding.UTF8) + ".xls");
// 添加头信息，指定文件大小，让浏览器能够显示下载进度
// System.Web.HttpContext.Current.Response.AddHeader("Content-Length",sb.ToString());

// 指定返回的是一个不能被客户端读取的流，必须被下载
System.Web.HttpContext.Current.Response.ContentType = "application/ms-excel";

// 把文件流发送到客户端
System.Web.HttpContext.Current.Response.Write(sb.ToString());
// 停止页面的执行

System.Web.HttpContext.Current.Response.End();
}