• ASP.NET 实现文件下载


    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

    View Code
    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

    View Code
    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 :

    View Code
    <%@ 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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  • 原文地址:https://www.cnblogs.com/suizhouqiwei/p/2545882.html
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