在日常项目中，我们经常用到文件的上传下载功能，今天分享一个在ASP.NET中下载文件的例子，通过实现IHttpHandler 来实现下载。
直接上代码：
DownloadHandler.cs
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public class DownloadHandler:IHttpHandler { public bool IsReusable { get { return true; } } public void ProcessRequest(HttpContext context) { HttpResponse Response = context.Response; HttpRequest Request = context.Request; System.IO.Stream iStream = null; byte[] buffer = new Byte[10240]; int length; long dataToRead; try { string filename = FileHelper.Decrypt(Request["fn"]); //通过解密得到文件名 string filepath = HttpContext.Current.Server.MapPath("~/") + "files/" + filename; //待下载的文件路径 iStream = new System.IO.FileStream(filepath, System.IO.FileMode.Open, System.IO.FileAccess.Read, System.IO.FileShare.Read); Response.Clear(); dataToRead = iStream.Length; long p = 0; if (Request.Headers["Range"] != null) { Response.StatusCode = 206; p = long.Parse(Request.Headers["Range"].Replace("bytes=", "").Replace("-", "")); } if (p != 0) { Response.AddHeader("Content-Range", "bytes " + p.ToString() + "-" + ((long)(dataToRead - 1)).ToString() + "/" + dataToRead.ToString()); } Response.AddHeader("Content-Length", ((long)(dataToRead - p)).ToString()); Response.ContentType = "application/octet-stream"; Response.AddHeader("Content-Disposition", "attachment; filename=" + System.Web.HttpUtility.UrlEncode(System.Text.Encoding.GetEncoding(65001).GetBytes(Path.GetFileName(filename)))); iStream.Position = p; dataToRead = dataToRead - p; while (dataToRead > 0) { if (Response.IsClientConnected) { length = iStream.Read(buffer, 0, 10240); Response.OutputStream.Write(buffer, 0, length); Response.Flush(); buffer = new Byte[10240]; dataToRead = dataToRead - length; } else { dataToRead = -1; } } } catch (Exception ex) { Response.Write("Error : " + ex.Message); } finally { if (iStream != null) { iStream.Close(); } Response.End(); } } }
FileHelper.cs
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public class FileHelper { public static string Encrypt(string filename) { byte[] buffer = HttpContext.Current.Request.ContentEncoding.GetBytes(filename); return HttpUtility.UrlEncode(Convert.ToBase64String(buffer)); } public static string Decrypt(string encryptfilename) { byte[] buffer = Convert.FromBase64String(encryptfilename); return HttpContext.Current.Request.ContentEncoding.GetString(buffer); } }
在web.config的<handlers> 节点中添加
<add name="download" verb="*" path="download.aspx" type="SinoOcean.Seagull2.Questionnaire.Common.DownloadHandler" />
path 下载页面的路径。
verb 谓词 请求的方式 http ftp get post 等。设置为* 代表所有。
type 类型 SinoOcean.Seagull2.Questionnaire.Common.DownloadHandler SinoOcean.Seagull2.Questionnaire.Common 命名空间 DownloadHandler 类名
在项目中添加 download.aspx 页面 去掉后台代码文件 download.aspx.cs
aspx页面如下 ：
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<%@ Page Language="C#" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
在项目中创建一个文件夹 files
使用 下载功能：
string url = FileHelper.Encrypt("文件名称");
Response.Redirect("~/download.aspx?fn=" + url);
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