Asp.net给站点某目录增加Aspnet用户

using system;
using system.data;
using system.configuration;
using system.collections;
using system.web;
using system.web.security;
using system.web.ui;
using system.web.ui.webcontrols;
using system.web.ui.webcontrols.webparts;
using system.web.ui.htmlcontrols;

using system.io;
using system.net;
using system.security.accesscontrol;
using system.security.principal;

public partial class aclchange : system.web.ui.page
{
    //文件夹路径
    private string strdir = "images";

    protected void page_load(object sender, eventargs e)
    {
        if (!ispostback)
        {
            adddirectorysecurity();
        }
    }

    /// <summary>
    /// 给文件夹添加aspnet用户
    /// </summary>
    private void adddirectorysecurity()
    {
        directoryinfo dirinfo = new directoryinfo(server.mappath(strdir));

        if ((dirinfo.attributes & fileattributes.readonly) != 0)
        {
            dirinfo.attributes = fileattributes.normal;
        }

        //取得访问控制列表
        directorysecurity dirsecurity = dirinfo.getaccesscontrol();

        string strdomain = dns.gethostname();

        dirsecurity.addaccessrule(new filesystemaccessrule(strdomain + "\\aspnet", filesystemrights.fullcontrol, accesscontroltype.allow));

        dirinfo.setaccesscontrol(dirsecurity);
    }
}