asp.net点击下载图片 C#

DownloadFile.aspx页面内容:

<%@ Page Language="C#" %>

<%

//使用方法
DownloadFile.aspx?file=要下载的图片

string url = HttpContext.Current.Request.Url.Query.ToLower();

//file=dddd.jpg
url = url.Replace("?file=", "");

Response.BufferOutput = false;

Response.Clear();
Response.ContentType = "application/x-msdownload";
Response.AppendHeader("Content-Disposition", "attachment; filename=" + url);
Response.ContentType = "application/octstream";
Response.CacheControl = "Private";
System.IO.Stream stm = new System.IO.FileStream(Server.MapPath(url), System.IO.FileMode.Open, System.IO.FileAccess.Read, System.IO.FileShare.Read);
Response.AppendHeader("Content-length", stm.Length.ToString());

System.IO.BinaryReader br = new System.IO.BinaryReader(stm);

byte[] bytes;

for (Int64 x = 0; x < (br.BaseStream.Length / 4096 + 1); x++)
{
bytes = br.ReadBytes(4096);
Response.BinaryWrite(bytes);
System.Threading.Thread.Sleep(5); //休息一下,防止耗用带宽太多。
}

stm.Close();

%>