ASP.Net下載大文件的實現方法

本文實例講述了ASP.Net下載大文件的實現方法。分享給大家供大家參考。具體分析如下：

當我們的網站需要支持下載大文件時，如果不做控制可能會導致用戶在訪問下載頁面時發生無響應，使得浏覽器崩潰。可以參考如下代碼來避免這個問題。

關於此代碼的幾點說明：

1. 將數據分成較小的部分，然後將其移動到輸出流以供下載，從而獲取這些數據。

2. 根據下載的文件類型來指定 Response.ContentType 。（參考OSChina的這個網址可以找到大部分文件類型的對照表：http://tool.oschina.net/commons）

3. 在每次寫完response時記得調用 Response.Flush()

4. 在循環下載的過程中使用 Response.IsClientConnected 這個判斷可以幫助程序盡早發現連接是否正常。若不正常，可以及早的放棄下載，以釋放所占用的服務器資源。

5. 在下載結束後，需要調用 Response.End() 來保證當前線程可以在最後被終止掉。

復制代碼 代碼如下:
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();
            }
        }
    }
}

希望本文所述對大家的asp.net程序設計有所幫助。