在网页上下载文件

原链接：https://www.cnblogs.com/wangdetian168/articles/1216690.html

如图：下面代码是文件较小时的代码，用着没问题，但是文件超过了1G后发现下载出错了，找到了上面链接的下载大文件的代码，修改过后竟然能用。

 

 

 源码：

//FileStreamResult:小文件下载时返回的数据类型
        public void DownloadBackup(string id)
        {
            //try
            //{
            //    var data = this.CreateService<IDbBackupAppService>().GetOne(id);
            //    var path = Server.MapPath("~/Resource/DbBackup/" + data.F_FileName);
            //    var name = Path.GetFileName(path);
            //    //文件过大（> 1G）时下面代码抛出异常：算术运算中发生溢出或下溢
            //    return File(new FileStream(path, FileMode.Open), "application/octet-stream", Server.UrlEncode(name));
            //}
            //catch (Exception ex)
            //{
            //    Sys_Log entity = this.InsertLog(LogType.Exception, "系统管理/数据备份", "下载备份文件异常，异常信息[" + ex.Message + "]");
            //    this.CreateService<ILogAppService>().insertLog(entity);
            //    throw new Exception(ex.ToString());
            //}
            Debug.WriteLine("开始时间:" + DateTime.Now);
            //文件过大（>1G）处理
            var data = this.CreateService<IDbBackupAppService>().GetOne(id);
            var filepath = Server.MapPath("~/Resource/DbBackup/" + data.F_FileName);
            Stream iStream = null;
            byte[] buffer = new Byte[102400];
            int length;
            //总共要读取的字节长度
            long dataToRead;
            string filename = Path.GetFileName(filepath);
            try
            {
                //打开文件
                iStream = new FileStream(filepath, FileMode.Open, FileAccess.Read, FileShare.Read);
                dataToRead = iStream.Length;

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

                //读取文件
                while (dataToRead > 0)
                {
                    //验证客户端是否链接
                    if (Response.IsClientConnected)
                    {
                        //读取数据到buffer里
                        length = iStream.Read(buffer, 0, 102400);
                        //把buffer中的数据写入到输出流
                        Response.OutputStream.Write(buffer, 0, length);
                        //刷新
                        Response.Flush();
                        buffer = new Byte[102400];
                        dataToRead = dataToRead - length;
                    }
                    else
                    {
                        //防止无限循环
                        dataToRead = -1;
                    }
                }
            }
            catch (Exception ex)
            {
                //捕捉异常信息
                Response.Write("Error : " + ex.Message);
                Sys_Log entity = this.InsertLog(LogType.Exception, "系统管理/数据备份", "下载备份文件异常，异常信息[" + ex.Message + "]");
                this.CreateService<ILogAppService>().insertLog(entity);
                //throw new Exception(ex.ToString());
            }
            finally
            {
                if (iStream != null)
                {
                    //关闭文件
                    iStream.Close();
                }
            }
            Debug.WriteLine("结束时间:" + DateTime.Now);
        }