C# web 下载大文件代码

 public bool Down(string filepath, string code)
        {
            bool succ = false;

            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();
                }
            }

            return succ;
        }