using System.IO;

1.文件上传
----------
如下要点：
HTML部分：
<form id="form1" runat="server" method="post" enctype="multipart/form-data">
<input id="FileUpLoad" type="file" runat="server"/><br />
后台CS部分 按钮事件
//string strFileFullName = System.IO.Path.GetFileName(this.FileUpLoad.PostedFile.FileName);
//this.FileUpLoad.PostedFile.SaveAs(Server.MapPath("./xmlzip/") + strFileFullName);

2.文件下载
----------
ListBox的SelectedIndexChanged事件 设定相关下载连接
    protected void lst_DownLoadFileList_SelectedIndexChanged(object sender, EventArgs e)
    {
        try
        {
            string strJS = "window.open(xmlzip/";
            strJS += this.lst_DownLoadFileList.SelectedItem.Text.Trim();
            strJS += "); return false; ";
            this.imgbtn_DownLoadFile.Attributes.Add("onclick", strJS);
        }
        catch (Exception ex)
        {
            ex.ToString();
        }
    }
或者也可以通过 改变Label的Text值 来实现点击后实现文件下载的超级连接
this.Label1.Text = "<a href=\"xmlzip/a.rar\">a.rar</a>"

3.文件删除
---------
string strFilePath = Server.MapPath("../CountryFlowMgr/xmlzip/"+this.lst_DownLoadFileList.SelectedItem.Text.Trim());
if (File.Exists(strFilePath))
{
   File.Delete(strFilePath);
   if (File.Exists(strFilePath))
   {
 Response.Write("ok");
   }
   else
   {
        Response.Write("ok");
   }
}

4.得到文件夹下的文件列表
-----------
#region 得到当前可用的文件列表
    /// <summary>
    /// 得到当前可用的文件列表
    /// </summary>
    /// <param name="IsAlert">是否需要弹出提示信息</param>
    private void fn_getCurrFileList(bool IsAlert)
    {
        try
        {
            //查找xmlzip文件夹下 属于其本身UnitCoding的相关zip文件
            string strXmlZipDirectory = Server.MapPath("../xmlzip/");
            if (Directory.Exists(strXmlZipDirectory))
            {
                //DirectoryInfo di = new DirectoryInfo(Environment.CurrentDirectory);
                DirectoryInfo di = new DirectoryInfo(strXmlZipDirectory);
               
                FileInfo[] FI = di.GetFiles("*.zip");//只查.zip文件
                if (FI.Length > 0)
                {
                    lst_DownLoadFileList.Items.Clear();
                    foreach (FileInfo tmpFI in FI)
                    {
                        ListItem tmpItem = new ListItem();
                        tmpItem.Text = tmpFI.Name;
                        lst_DownLoadFileList.Items.Add(tmpItem);
                    }
                    lst_DownLoadFileList.SelectedIndex = 0;
                }
                else
                {
                    if (IsAlert)
                    {
                        Response.write("查无可以下载的文件!");
                    }
                }
            }
        }
        catch (Exception ex)
        {
            ex.ToString();
        }
    }
    #endregion
更多更详细的以后再做补充

http://www.cnblogs.com/freeliver54/archive/2007/01/18/623697.html