ASP.net实现文件下载

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。

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=CodeShark.zip");

string filename = 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。

protected void Button2_Click(object sender, EventArgs e)

...{

string fileName = "CodeShark.zip";//客户端保存的文件名

string filePath = Server.MapPath("DownLoad/CodeShark.doc");//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();

}
方式三：WriteFile分块下载

protected void Button3_Click(object sender, EventArgs e)

...{

string fileName = "CodeShark.zip";//客户端保存的文件名

string filePath = Server.MapPath("DownLoad/CodeShark.zip");//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();

}

}
方式四：流方式下载

protected void Button4_Click(object sender, EventArgs e)

...{

string fileName = "CodeShark.zip";//客户端保存的文件名

string filePath = Server.MapPath("DownLoad/CodeShark.zip");//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();

}

第一个方法我测试过，没问题，但是我没有测试超过400MB的内容。其余三个方法我自己没具体测试。