C#实现文件下载的几种方式

先把有问题的代码贴出来吧,

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.IO;

namespace infoPlatClient.NetDisk
{
public partial class downLoad : Com.DRPENG.Common.WebStruct.BaseForm
{

/// <summary>
/// 取得要下载文件的路径
/// </summary>
private string fileRpath
{
get
{
return Request["fileRpath"] == null ? "" : Request["fileRpath"];
}
}
/// <summary>
/// 取得要下载文件的名称
/// </summary>

protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
this.DownloadFile();
}
public void DownloadFile()
{

Response.ClearHeaders();
Response.Clear();
Response.Expires = 0;
Response.Buffer =true;
Response.AddHeader("Accept-Language", "zh-tw");
string name = System.IO.Path.GetFileName(fileRpath);
System.IO.FileStream files = new FileStream(fileRpath, FileMode.Open, FileAccess.Read, FileShare.Read);
byte[] byteFile=null;
if (files.Length == 0)
{
byteFile=new byte[1];
}
else
{
byteFile = new byte[files.Length];
}
files.Read(byteFile, 0, (int)byteFile.Length);
files.Close();

Response.AddHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(name, System.Text.Encoding.UTF8));
Response.ContentType = "application/octet-stream;charset=gbk";
Response.BinaryWrite(byteFile);
Response.End();

}
}
}

之前一直用这种下载方式，可是有一次用户上传了一个700Mb的文件时报内存溢出的问题，分析了一下原因，用户的内存只有256M，而下载文件时要创建内存流，导致了内存溢出。

解决方案:1>WriteFile分块下载，就是每次下载指定数量的多件;

2>通过超链接的方式;

lblDownLoad.Text = "<a href='" + drv["VPath"].ToString() + "'>下载</a>"

下面是四种实现文件下载的方式:

using System;
using System.Data;
using System.Configuration;
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.IO;

public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{

}

//TransmitFile实现下载
protected void Button1_Click(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：
*/

Response.ContentType = "application/x-zip-compressed";
Response.AddHeader("Content-Disposition", "attachment;filename=z.zip");
string filename = Server.MapPath("DownLoad/z.zip");
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();

}
}