aspnet

C#从服务器下载文件可以使用下面4个方法：TransmitFile、WriteFile、WriteFile和流方式下载文件，并保存为相应类型，方法如下：

1、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);

}

2、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();

}

3、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();

}

}

4、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();

}