c# 4.0 - 一旦大小小于缓冲区长度 c#，下载就不起作用

今天，在执行下载大尺寸文件的逻辑时，我遇到了一个错误。为了下载我的逻辑，将文件分成 10KB 块，然后集成它并正在下载。虽然下载发生的事情就像每次将总大小减少 10KB ，但是一旦剩余长度小于 10KB，我的下载就会中断。请找到我的以下代码，如果我的逻辑需要任何更改，请告诉我。

protected void btnDownload_Click(object sender, EventArgs e)
    {
        SPSecurity.RunWithElevatedPrivileges(delegate()
        {
            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 = "C:''Users''GZT00000000000001020''Desktop''123.zip";
            // Identify the file name.
            string filename = System.IO.Path.GetFileName(filepath);
            try
            {
                iStream = new System.IO.FileStream(filepath, System.IO.FileMode.Open, System.IO.FileAccess.Read, System.IO.FileShare.Read);
                dataToRead = iStream.Length;
                Page.Response.ContentType = "application/octet-stream";
                Page.Response.AddHeader("Content-Disposition", "attachment; filename=" + filename);
                // Read the bytes.
                while (dataToRead > 0)
                {
                    // Verify that the client is connected.
                    if (Page.Response.IsClientConnected)
                    {
                        if( (dataToRead < 10000) && (dataToRead!=-1))
                        {
                            length = (int)dataToRead;
                            buffer = new Byte[length];
                            dataToRead = -1;
                        }
                        else
                        {
                            // Read the data in buffer.
                            length = iStream.Read(buffer, 0, 10000);
                        }
                        // Write the data to the current output stream.
                        Page.Response.OutputStream.Write(buffer, 0, length);
                        // Flush the data to the HTML output.
                        Page.Response.Flush();
                        if (dataToRead > 10000)
                        {
                            buffer = new Byte[10000];
                            dataToRead = dataToRead - length;
                        }
                        else if(dataToRead!=-1)
                        {
                            length =(int)dataToRead ;
                            buffer = new Byte[length];
                        }                         
                    }
                    else
                    {
                        //prevent infinite loop if user disconnects
                        dataToRead = -1;
                    }
                }
            }
            catch (Exception ex)
            {
                // Trap the error, if any.
                Page.Response.Write("Error : " + ex.Message);
            }
            finally
            {
                if (iStream != null)
                {
                    //Close the file.
                    iStream.Close();
                }
                Page.Response.Close();
            }
        });
    }