问缓存Active Directory数据

EN

public class UserInfo
{
    public static List<UserInfo> UserInfoCache { 
        get{
            if(HttpContext.Current.Cache["CachedUserList"] == null) {
                PrincipalContext ctx = new PrincipalContext(ContextType.Domain);

                PrincipalSearcher ps = new PrincipalSearcher(new UserPrincipal(ctx) { SamAccountName = "*" });

                var users = ps.FindAll();

                var result = from c in users
                             let u = (UserPrincipal)c
                             select new UserInfo() { Email = u.EmailAddress, FirstName = u.GivenName, LastName = u.Surname };

                HttpContext.Current.Cache.Insert("CachedUserList", result, null, DateTime.Now.AddHours(12), System.Web.Caching.Cache.NoSlidingExpiration);
            }

            return (List<UserInfo>)HttpContext.Current.Cache["CachedUserList"];
        }
    }

    public string Email { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
}