asp.net文件下载

asp.net2.0以后，我们有了很多种文件下载的选择。

//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();
        }
    }   

以上除了第四种不推荐以外，其他的都可以，但是个人感觉分块下载的要好一点。没有仔细测试，所以可能有问题。

注意：对于中文文件名要编码才能正确显示。对于长中文文件名(UTF8编码后大于153字节的中文)即使编码了，还是有问题的，大家可以参考这个链接。 http://hi.baidu.com/river_5566/blog/item/d66804cef8afb031b700c863.html