Implementation and code of ASP. NET large file download, asp.net File Download

Implementation and code of ASP. NET large file download, asp.net File Download

File Download is the most basic function of a website, ASP. NET website file download function implementation is also very simple, but if you encounter large file download without special processing, it will have unpredictable consequences. This article provides implementation ideas and code for large file downloads Based on ASP. NET.

When our website needs to support downloading large files, if it is not controlled, it may cause a user to have no response when accessing the download page, causing the browser to crash. You can refer to the following code to avoid this problem.

using System;namespace WebApplication1{    public partial class DownloadFile : System.Web.UI.Page    {        protected void Page_Load(object sender, EventArgs e)        {            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 = Server.MapPath("/") +"./Files/TextFile1.txt";            // 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.Clear();                Response.ClearHeaders();                Response.ClearContent();                Response.ContentType = "text/plain"; // Set the file type                Response.AddHeader("Content-Length", dataToRead.ToString());                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();                }                Response.End();            }        }    }}

　　Several notes about this Code:

1. Divide the data into smaller parts and move it to the output stream for download to obtain the data.

2. Specify Response. ContentType Based on the downloaded file type. (Refer to the OSChina URL to find the comparison table for most file types: http://tool.oschina.net/commons)

3. Remember to call response. Flush () every time you finish writing Response ()

4. Using Response. IsClientConnected in the loop download process can help the program detect whether the connection is normal as soon as possible. If it is abnormal, You can discard the download as soon as possible to release the occupied server resources.

5. After the download is complete, call Response. End () to ensure that the current thread can be terminated.