"Attempted to perform an unauthorized operation" when using CustomRoleProvider

Question

I've wrote a Custom Role Provider :

public class CustomRoleProvider : RoleProvider
{

        public override string[] GetRolesForUser(string username)
        {

            var rolesService = ObjectFactory.GetInstance<IRoleService>();
            return rolesService.GetRolesForUser(username.ToInt());
        }

        public override bool IsUserInRole(string username, string roleName)
        {
            var rolesService = ObjectFactory.GetInstance<IRoleService>();
            return rolesService.IsUserInRole(username.ToInt(), roleName);
        }

        //....
}

and registered in web.config :

<roleManager enabled="true" defaultProvider="CustomRoleProvider">
      <providers>
        <clear/>
        <add name="CustomRoleProvider" 
           type="PooyanTKD.Web.Infrastructure.CustomRoleProvider" 
           connectionStringName="DefaultConnection"
           enablePasswordRetrieval="false" enablePasswordReset="true" 
           requiresQuestionAndAnswer="false" writeExceptionsToEventLog="false" />
      </providers>
</roleManager>

And I've wrote a Custom Authorize Attribute :

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, Inherited = true, AllowMultiple = true)]
    public class SiteAuthorizeAttribute : AuthorizeAttribute
    {
        protected override void HandleUnauthorizedRequest(AuthorizationContext filterContext)
        {
            if (filterContext.HttpContext.Request.IsAuthenticated)
            {
                throw new UnauthorizedAccessException(); //to avoid multiple redirects
            }
            else
            {
                base.HandleUnauthorizedRequest(filterContext);
            }
        }
    } 

but when I decorate my Controller or action method with [SiteAuthorize(Roles="Admins")] after login I'm getting this error :

Attempted to perform an unauthorized operation.

Source Error :

Line 14:             if (filterContext.HttpContext.Request.IsAuthenticated)
Line 15:             {
Line 16:                 throw new UnauthorizedAccessException(); //to avoid multiple redirects
Line 17:             }
Line 18:             else

I've trouble finding out my problem and screwed me up, can anyone help me to figure out where is my problem?
PS : when I check value of User.Identity.Name in other view it's 0, also I check my authentication type in web.config :

<forms name="Sir1Afifi2013"
               cookieless="UseCookies"
               loginUrl="~/Account/LogOn"
               defaultUrl="~/Admin/Main"
               slidingExpiration="true"
               protection="All"
               path="/"
               timeout="20" />
</authentication>

Thanks in Advance

Answer 1

finally I solved my problem using redirecting Unauthorized user to another route this way :

protected override void HandleUnauthorizedRequest(AuthorizationContext filterContext)
        {
            if (filterContext.HttpContext.Request.IsAuthenticated)
            {
                filterContext.Result = new RedirectToRouteResult(new RouteValueDictionary(new
                {
                    action = "Index",
                    controller = "Home",
                    area = ""
                }));
            }
            else
            {
                base.HandleUnauthorizedRequest(filterContext);
            }
        }