Asp.Net文件下载

<%@ WebHandler Language="C#" Class="AttachmentHandler" %>



using System;

using System.Collections.Generic;

using System.Web;

using System.Data.SqlClient;

using System.Configuration;



public class AttachmentHandler : IHttpHandler

{

    public void ProcessRequest(HttpContext context)

    {

        string workflowID = context.Request["guid"];

        string tableName = context.Request["tb"];



        if (string.IsNullOrEmpty(workflowID) || string.IsNullOrEmpty(tableName))

            context.Response.End();



        using (SqlConnection conn = new SqlConnection(ConfigurationManager.AppSettings["db"]))

        {

            conn.Open();

            var cmdText = string.Format(@"select FileName,Attachment from {0} where WorkflowID='{1}'"

                , tableName, workflowID);

            SqlCommand cmd = new SqlCommand(cmdText, conn);

            SqlDataReader dr = cmd.ExecuteReader();

            if (dr.Read())

            {

                if (!Convert.IsDBNull(dr["Attachment"]))

                {

                    context.Response.BinaryWrite((byte[])dr["Attachment"]);

                    context.Response.AppendHeader("Content-Disposition"

                        , string.Format("attachment;filename={0}"

                        , HttpUtility.UrlEncode(dr["FileName"].ToString())));

                }



                dr.Close();

                dr = null;

                context.Response.End();

            }



            conn.Close();

        }





    }



    public bool IsReusable

    {

        get

        {

            return false;

        }

    }

}

Ref:TransmitFile

View Code

    //TransmitFile实现下载

         protected void Button1_Click1(object sender, EventArgs e)

        {

            /*

             微软为Response对象提供了一个新的方法TransmitFile来解决使用Response.BinaryWrite

             下载超过400mb的文件时导致Aspnet_wp.exe进程回收而无法成功下载的问题。

             代码如下：

             */

            string strFileName = "xxx.ppt";

            Response.ContentType = "application/x-zip-compressed";

            //Response.ContentEncoding = System.Text.Encoding.GetEncoding("gb2312");

            string filename = BLL.Config.PART_EM_UPLOAD_DOC + strFileName;



            //BLL.Config.PART_EM_UPLOAD_DOC 为路径   ("D:/EMUploadDoc/")

            Response.AddHeader("Content-Disposition", "attachment;filename=" +Server.UrlPathEncode(strFileName));



           //Server.UrlPathEncode()解决文件名的乱码问题.

           

            Response.TransmitFile(filename);

        }    

//WriteFile实现下载

    protected void Button2_Click(object sender, EventArgs e)

    {

        /*

         using System.IO;

       

         */



        string fileName = "asd.txt";//客户端保存的文件名

        string filePath = Server.MapPath("DownLoad/aaa.txt");//路径



        FileInfo fileInfo = new FileInfo(filePath);

        Response.Clear();

        Response.ClearContent();

        Response.ClearHeaders();

        Response.AddHeader("Content-Disposition", "attachment;filename=" + fileName);

        Response.AddHeader("Content-Length", fileInfo.Length.ToString());

        Response.AddHeader("Content-Transfer-Encoding", "binary");

        Response.ContentType = "application/octet-stream";

        Response.ContentEncoding = System.Text.Encoding.GetEncoding("gb2312");

        Response.WriteFile(fileInfo.FullName);

        Response.Flush();

        Response.End();

    }



      //WriteFile分块下载

    protected void Button3_Click(object sender, EventArgs e)

    {



        string fileName = "aaa.txt";//客户端保存的文件名

        string filePath = Server.MapPath("DownLoad/aaa.txt");//路径



        System.IO.FileInfo fileInfo = new System.IO.FileInfo(filePath);



        if (fileInfo.Exists == true)

        {

            const long ChunkSize = 102400;//100K 每次读取文件，只读取100Ｋ，这样可以缓解服务器的压力

            byte[] buffer = new byte[ChunkSize];



            Response.Clear();

            System.IO.FileStream iStream = System.IO.File.OpenRead(filePath);

            long dataLengthToRead = iStream.Length;//获取下载的文件总大小

            Response.ContentType = "application/octet-stream";

            Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName));

            while (dataLengthToRead > 0 && Response.IsClientConnected)

            {

                int lengthRead = iStream.Read(buffer, 0, Convert.ToInt32(ChunkSize));//读取的大小

                Response.OutputStream.Write(buffer, 0, lengthRead);

                Response.Flush();

                dataLengthToRead = dataLengthToRead - lengthRead;

            }

            Response.Close();

        }

    }



    //流方式下载

    protected void Button4_Click(object sender, EventArgs e)

    {

        string fileName = "aaa.txt";//客户端保存的文件名

        string filePath = Server.MapPath("DownLoad/aaa.txt");//路径



        //以字符流的形式下载文件

        FileStream fs = new FileStream(filePath, FileMode.Open);

        byte[] bytes = new byte[(int)fs.Length];

        fs.Read(bytes, 0, bytes.Length);

        fs.Close();

        Response.ContentType = "application/octet-stream";

        //通知浏览器下载文件而不是打开

        Response.AddHeader("Content-Disposition", "attachment;  filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));

        Response.BinaryWrite(bytes);

        Response.Flush();

        Response.End();



    }