public void DownFile(string filePath ,string fileName )
{
 // filePath 文件路径 例如：/File/记录.xlsx 
 // fileName 文件名称 例如：记录.xlsx （要后缀哦）
Encoding encoding; // 申明编码
string outputFileName; // 输出名字
Debug.Assert(HttpContext.ApplicationInstance.Request.UserAgent != null, "HttpContext.ApplicationInstance.Request.UserAgent != null");
string browser = HttpContext.ApplicationInstance.Request.UserAgent.ToUpper();
// 微软的浏览器和ie过滤
if (browser.Contains("MS") && browser.Contains("IE"))
{
outputFileName = HttpUtility.UrlEncode(filePath);
encoding = Encoding.Default;
}
//火狐
else if (browser.Contains("FIREFOX"))
{
outputFileName = fileName;
encoding = Encoding.GetEncoding("GB2312");
}
else
{
outputFileName = HttpUtility.UrlEncode(fileName);
encoding = Encoding.Default;
}
string absoluFilePath = Server.MapPath(filePath); //获取上传文件路径
FileStream fs = new FileStream(absoluFilePath, FileMode.Open);
byte[] bytes = new byte[(int)fs.Length];
fs.Read(bytes, 0, bytes.Length);
fs.Close(); //关闭流，释放资源
HttpContext.ApplicationInstance.Response.Clear();
HttpContext.ApplicationInstance.Response.Buffer = true;
HttpContext.ApplicationInstance.Response.ContentEncoding = encoding;
HttpContext.ApplicationInstance.Response.AddHeader("Content-Disposition", string.Format("attachment; filename={0}", string.IsNullOrEmpty(outputFileName) ? DateTime.Now.ToString("yyyyMMddHHmmssfff") : outputFileName));
Response.BinaryWrite(bytes);
Response.Flush();
HttpContext.ApplicationInstance.Response.End();
}