使用ActionFilterAttribute时如何防止缓存

Question

I have created the following action filter class:-

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
    public class CheckUserPermissionsAttribute : ActionFilterAttribute
    {
        Repository repository = new Repository();
        public string Model { get; set; }
        public string Action { get; set; }

public override void OnActionExecuting(ActionExecutingContext filterContext)
        {
            string ADusername = filterContext.HttpContext.User.Identity.Name.Substring(filterContext.HttpContext.User.Identity.Name.IndexOf("\\") + 1);
            if (!repository.can(ADusername,Model,Action)) 
            {
filterContext.Result = new HttpUnauthorizedResult("You cannot access this page");

            }

base.OnActionExecuting(filterContext);
        }
    }

Which will call the following model repository class:-

public bool can(string user, string Model, string Action) {
if (Model == "Admin")
            {
bool isadminByuser =  tms.SecurityRoles.Where(a => a.Name == "Administrator").SingleOrDefault().SecurityRoleUsers.Any(a => a.UserName.ToLower() == user.ToLower());
var adminByGroup = tms.SecurityRoles.Where(a => a.Name == "Administrator").SingleOrDefault().Groups.Select(a2 => a2.TMSUserGroups.Where(a3 => a3.UserName.ToLower() == user.ToLower()));
bool isadminByGroup = adminByGroup.Count() >= 1;
if (isadminByGroup || isadminByuser) 
{

                    return true;
                }
            }
            return false;

        }

The above will work fine, but if I change the database values then the repository values; isadminByuser & adminByGroup, Will have the same values (cached values). but if I stop the project and re-build and run the project again from visual studio I will get the right values. So can anyone advice if I am have a caching problem , which is forcing the repository to have the same values unless re-run the project?

Thanks

Answer 1

You can use like this..

[NoCache]
public ActionResult Ex()
{
    //enter code here
}

or

[OutputCache(NoStore = true, Duration = 0, VaryByParam = "None")] 
public ActionResult Ex()
{
   //enter code here
}

Hope it helps...

Answer 2

I assume that you use Entity Framework and one repository instance creates one EF context.

Action filters can be reused for multiple requests so the EF context is reused. We you use the same EF context for multiple queries to an entity, the entity is actually reused (something like a cache).

Possible solutions:

1. Change the MergeOption
2. call Refresh()
3. use AsNoTracking()

4. Preferred solution Do not reuse the context so that you get the latest data and your context doesn't keep more and more entities in memory.

    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)] public class CheckUserPermissionsAttribute : ActionFilterAttribute { public override void OnActionExecuting(ActionExecutingContext filterContext) { Repository repository = new Repository(); //create the repository here if (!repository.can(ADusername,Model,Action)) { ... 

Side notes:

1. using NoTracking (MergeOption.NoTracking or AsNoTracking) increases performance See here
2. The solutions are not mutually exclusive. You can apply solution 3 and 4 without any problem