C# 文件上传，下载解决方案

//第一步，将文件名，路径单独存入一张表，（为防止文件重复，路径后加一个guid命名的文件夹）
protected void btnSave_Click(object sender, EventArgs e)
        {
            if (!File1.HasFile)
            {
                Alert("请选择文件！");
                return;
            }

            string filename = File1.FileName;
            string savedPath = System.Configuration.ConfigurationManager.AppSettings["UploadFilePath"] + Guid.NewGuid().ToString("N");

            try
            {
                File1.SaveAs(Server.MapPath(savedPath));
            }
            catch
            {
                Alert("文件上传失败！");
                return;
            }

            string guid = EFContext.Current.ISystemService.ISysFileService.Upload(filename, savedPath, int.Parse(EFContext.Current.UserIdentity));

            AddFile(guid);

        }

 DbCommand dbc = SqlDB.GetStoredProcCommand(sqlCommand);
            SqlDB.AddInParameter(dbc, "Name", SqlDbType.NVarChar, entity.Name);
            SqlDB.AddInParameter(dbc, "Url", SqlDbType.NVarChar, entity.Url);
            SqlDB.AddInParameter(dbc, "Created", SqlDbType.DateTime, entity.Created);
            SqlDB.AddInParameter(dbc, "CreatedBy", SqlDbType.Int, entity.CreatedBy);
            SqlDB.AddOutParameter(dbc, "Id", SqlDbType.Char,36);

返回guid存入存放文件详细信息的表中
下载文件时根据此guid去读取文件路径和文件名

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using Microsoft.Practices.Unity;
using System.Text;
using WelderQualification.Models;

namespace WelderQualification.Components
{
    public class FileDownloadHandler : EFDataHandler
    {
        public override void DataEvent(HttpContext context)
        {
            string guid = context.Request.QueryString["guid"];
            if (string.IsNullOrEmpty(guid))
                return;
            guid = guid.Trim();
            if (guid.Length != 36)
                return;

            SysFileInfo info=EFContext.Current.ISystemService.ISysFileService.Get(guid);
            if(info==null||info.CreatedBy==0)
                return;
            
            System.IO.FileInfo fileInfo = new System.IO.FileInfo(context.Server.MapPath(info.Url));

            if (fileInfo.Exists)
            {
                int ChunkSize = 102400;//100K 每次读取文件，只读取100K，这样可以缓解服务器的压力
                byte[] buffer = new byte[ChunkSize];

                context.Response.Clear();
                System.IO.FileStream iStream = System.IO.File.OpenRead(fileInfo.FullName);
                long dataLengthToRead = iStream.Length;//获取下载的文件总大小
                context.Response.ContentType = "application/octet-stream";
                context.Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(info.Name));
                while (dataLengthToRead > 0 && context.Response.IsClientConnected)
                {
                    int lengthRead = iStream.Read(buffer, 0, ChunkSize);//读取的大小
                    context.Response.OutputStream.Write(buffer, 0, lengthRead);
                    context.Response.Flush();
                    dataLengthToRead = dataLengthToRead - lengthRead;
                }
                iStream.Close();
                context.Response.Close();
            }
        }
    }
}

见一个ashx页面：

<%@ WebHandler Language="C#" Class="WelderQualification.Components.FileDownloadHandler" %>

页面绑定

   <a href='/FileDownLoad.ashx?guid=<%# DataBinder.Eval(Container.DataItem, "Url")%>'
                                target="_blank">

这样就OK了。