Asp.net 下载大文件

Response.WriteFile致命的局限性。WriteFile 在获取文件的路径后，会试图将文件流全部读入内存，之后再发送回客户端。对于小文件和流量很小的网站，使用这个方法或许问题不大，但如果文件很大或者网站的流量很大，使用这个方法可以让 aspnet_wp.exe 进程意味终止，导致当前服务器下所有 asp.net 站点全部瘫痪，不仅如此，服务器的物理内存也会在瞬间被填满，导致其它程序运行失败或意外终止,使用下面代码可解决问题：

System.IO.Stream iStream = null;

// Buffer to read 10K bytes in chunk:
byte[] buffer = new Byte[10000];

// Length of the file:
int length;

// Total bytes to read:
long dataToRead;

// Identify the file to download including its path.
string filepath = "DownloadFileName";

// Identify the file name.
string filename = System.IO.Path.GetFileName(filepath);

try {
    // Open the file.
    iStream = new System.IO.FileStream(filepath, System.IO.FileMode.Open,
    System.IO.FileAccess.Read, System.IO.FileShare.Read);


    // Total bytes to read:
    dataToRead = iStream.Length;

    Response.ContentType = "application/octet-stream";
    Response.AddHeader("Content-Disposition", "attachment; filename=" + filename);

    // Read the bytes.
    while (dataToRead > 0) {
        // Verify that the client is connected.
        if (Response.IsClientConnected) {
            // Read the data in buffer.
            length = iStream.Read(buffer, 0, 10000);

            // Write the data to the current output stream.
            Response.OutputStream.Write(buffer, 0, length);

            // Flush the data to the HTML output.
            Response.Flush();

            buffer = new Byte[10000];
            dataToRead = dataToRead - length;
        } else {
            //prevent infinite loop if user disconnects
            dataToRead = -1;
        }
    }
} catch (Exception ex) {
    // Trap the error, if any.
    Response.Write("Error : " + ex.Message);
} finally {
    if (iStream != null) {
        //Close the file.
        iStream.Close();
    }
}