ASP.NET实现文件下载

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.OleDb;

public partial class download2 : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
int id = Convert.ToInt32(Request.QueryString["id"].ToString());
        OleDbDataReader dr = db.exe_dr("select * from 资料 where id=" + id);
        dr.Read();

        Response.Buffer = true;
        Response.Clear();
        Response.ContentType = dr["ContentType"].ToString();
        Response.AddHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(dr["name"].ToString()));
        Response.BinaryWrite((byte[])dr["file"]);
        Response.Flush();
        Response.End();
        db.conn.Close();
    }
}


方式一：TransmitFile实现下载。将指定的文件直接写入 HTTP 响应输出流，而不在内存中缓冲该文件。

protectedvoidButton1_Click(objectsender,EventArgse)
{
/**//*
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：
*/
Response.ContentType="application/x-zip-compressed";
Response.AddHeader("Content-Disposition","attachment;filename=CodeShark.zip");
stringfilename=Server.MapPath("DownLoad/CodeShark.zip");
Response.TransmitFile(filename);
}

方式二：WriteFile实现下载，将指定的文件直接写入 HTTP 响应输出流。注意：对大型文件使用此方法时，调用此方法可能导致异常。可以使用此方法的文件大小取决于 Web 服务器的硬件配置。

protectedvoidButton2_Click(objectsender,EventArgse)
{
stringfileName="CodeShark.zip";//客户端保存的文件名
stringfilePath=Server.MapPath("DownLoad/CodeShark.doc");//路径
FileInfofileInfo=newFileInfo(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();
}

方式三：WriteFile分块下载

protectedvoidButton3_Click(objectsender,EventArgse)
{
stringfileName="CodeShark.zip";//客户端保存的文件名
stringfilePath=Server.MapPath("DownLoad/CodeShark.zip");//路径
System.IO.FileInfofileInfo=newSystem.IO.FileInfo(filePath);
if(fileInfo.Exists==true)
{
constlongChunkSize=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=newbyte[ChunkSize];
Response.Clear();
System.IO.FileStreamiStream=System.IO.File.OpenRead(filePath);
longdataLengthToRead=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)
{
intlengthRead=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();
}
}

方式四：流方式下载

protectedvoidButton4_Click(objectsender,EventArgse)
{
stringfileName="CodeShark.zip";//客户端保存的文件名
stringfilePath=Server.MapPath("DownLoad/CodeShark.zip");//路径
//以字符流的形式下载文件
FileStreamfs=newFileStream(filePath,FileMode.Open);
byte[]bytes=newbyte[(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();
}