文件下载方法集合

最新推荐文章于 2022-07-12 15:51:15 发布

转载最新推荐文章于 2022-07-12 15:51:15 发布 · 366 阅读

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#stream #exception #buffer #object #byte #null

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本文介绍了ASP.NET中实现文件下载的五种不同方法，包括使用TransmitFile、WriteFile、OutputStream.Write分块下载、BinaryWrite一次性下载及BinaryWrite分块下载。每种方法均有详细的代码示例，并解释了其适用场景。

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public partial class FileDownLoad : System.Web.UI.Page
    {
        //提供下载的文件，不编码的话文件名会乱码
        private string fileName = HttpContext.Current.Server.UrlEncode("规范.rar");
        private string filePath = HttpContext.Current.Server.MapPath("规范.rar");
        //使用TransmifFile下载文件
        protected void btnDL1_Click(object sender, EventArgs e)
        {
            FileInfo info = new FileInfo(filePath);
            long fileSize = info.Length;
            Response.Clear();
            Response.ContentType = "application/x-zip-compressed";
            Response.AddHeader("Content-Disposition", "attachment;filename="+ fileName);
            //不指明Content-Length用Flush的话不会显示下载进度
            Response.AddHeader("Content-Length", fileSize.ToString());
            Response.TransmitFile(filePath, 0, fileSize);
            Response.Flush();
            Response.Close();
        }

        //使用WriteFile下载文件
        protected void btnDL2_Click(object sender, EventArgs e)
        {
            FileInfo info = new FileInfo(filePath);
            long fileSize = info.Length;
            Response.Clear();
            Response.ContentType = "application/octet-stream";
            Response.AddHeader("Content-Disposition", "attachement;filename=" + fileName);
            //指定文件大小
            Response.AddHeader("Content-Length", fileSize.ToString());
            Response.WriteFile(filePath, 0, fileSize);
            Response.Flush();
            Response.Close();
        }

        //使用OutputStream.Write分块下载文件
        protected void btnDL3_Click(object sender, EventArgs e)
        {
            //指定块大小
            long chunkSize = 102400;
            //建立一个100K的缓冲区
            byte[] buffer = new byte[chunkSize];
            //已读的字节数
            long dataToRead = 0;
            FileStream stream = null;
            try
            {
                //打开文件
                stream = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read);
                dataToRead = stream.Length;

                //添加Http头
                Response.ContentType = "application/octet-stream";
                Response.AddHeader("Content-Disposition", "attachement;filename=" + fileName);
                Response.AddHeader("Content-Length", dataToRead.ToString());

                while (dataToRead > 0)
                {
                    if (Response.IsClientConnected)
                    {
                        int length = stream.Read(buffer, 0, Convert.ToInt32(chunkSize));
                        Response.OutputStream.Write(buffer, 0, length);
                        Response.Flush();
                        Response.Clear();
                        dataToRead -= length;
                    }
                    else
                    {
                        //防止client失去连接
                        dataToRead = -1;
                    }
                }
            }
            catch (Exception ex)
            {
                Response.Write("Error:" + ex.Message);
            }
            finally
            {
                if (stream != null)
                {
                    stream.Close();
                }
                Response.Close();
            }
        }

        //使用BinaryWrite下载文件，大文件效率不行
        protected void btnDL4_Click(object sender, EventArgs e)
        {
            FileStream stream = null;
            try
            {
                //读文件,大文件一次读入会占用大量内存
                stream = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read);
                byte[] bytes = new byte[stream.Length];
                stream.Read(bytes, 0, bytes.Length);
                stream.Close();

                //添加Http头
                Response.ContentType = "application/octet-stream";
                Response.AddHeader("Content-Disposition", "attachement;filename=" + fileName);
                Response.AddHeader("Content-Length", bytes.Length.ToString());
                Response.BinaryWrite(bytes);
                Response.Flush();
            }
            catch (Exception ex)
            {
                Response.Write("Error:" + ex.Message);
            }
            finally
            {
                if (stream != null)
                {
                    stream.Close();
                }
                Response.Close();
            }
        }
        //使用BinaryWrite分块下载文件
        protected void btnDL5_Click(object sender, EventArgs e)
        {
            //指定区块和缓冲区
            long chunkSize = 102400;
            byte[] buffer = new byte[chunkSize];
            FileStream stream = null;
            long dataToRead = 0;
            try
            {
                stream = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read);
                dataToRead = stream.Length;
                //添加Http头
                Response.ContentType = "application/octet-stream";
                Response.AddHeader("Content-Disposition", "attachement;filename=" + fileName);
                Response.AddHeader("Content-Length", dataToRead.ToString());

                while (dataToRead > 0)
                {
                    if (Response.IsClientConnected)
                    {
                        int length = stream.Read(buffer, 0, Convert.ToInt32(chunkSize));
                        Response.BinaryWrite(buffer);
                        Response.Flush();
                        Response.Clear();

                        dataToRead -= length;
                    }
                    else
                    {
                        dataToRead = -1;
                    }
                }

            }
            catch(Exception ex)
            {
                Response.Write("Error:" + ex.Message);
            }
            finally
            {
                if (stream != null)
                {
                    stream.Close();
                }
                Response.Close();
            }
        }
    }