Hi Folks

I really need your help. Since a few days I have a big problem. It seems to me that all started with adding a new user group, but I'm not sure if that was the reason.

At the moment I get an error viewing my site remotely. This problem doesn't occur locally. The server error is:

...[ArgumentNullException: Value cannot be null. Parameter name: id] ...Umbraco.Core.Cache.DefaultRepositoryCachePolicy`2.GetEntityCacheKey(Object id)...

The underlying class seems to be my Navigation.cs which automatically finds some content nodes and builds the navigation.

public class NavigationController : SurfaceController
{
    private readonly string _culture;
    private const int NavigationLevel = 3;
    private int _navLevelCounter = 1;
    private const int CategoriesDataTypeId = 1115;

    public NavigationController()
    {
        _culture = Umbraco.ContentAtRoot().FirstOrDefault().GetCultureFromDomains();
    }

    public ActionResult Navigation()
    {
        var model = GetNavigationItems();

        return PartialView("~/Views/Partials/_navigation.cshtml", model);
    }

    private List<NavigationModel> GetNavigationItems()
    {
        var rootNavigationItems = new List<IPublishedContent>();
        var home = Umbraco.ContentAtRoot().FirstOrDefault();
        rootNavigationItems.Add(home);
        rootNavigationItems.AddRange(home.Children().Where(x => x.Value<bool>("isRoot") && !x.Value<bool>("hideInNavigation")).ToList());

        return rootNavigationItems.Select(GetNavigationModel).ToList();
    }

    private NavigationModel GetNavigationModel(IPublishedContent page)
    {

        var pageChildren = new List<IPublishedContent>();
        var childNavigationModels = new List<NavigationModel>();

        pageChildren = page.Children().Where(x => x.IsVisible() && !x.Value<bool>("isRoot") && !x.Value<bool>("hideInNavigation")).ToList();

        if (_navLevelCounter <= NavigationLevel && pageChildren.Any())
        {
            _navLevelCounter++;
            childNavigationModels = pageChildren
                .Select(GetNavigationModel)
                .OrderBy(x => x.Category)
                .ThenBy(x => x.CategoryOrderIndex)
                .ToList();
            _navLevelCounter--;
        }

        var rootParentId = !page.Value<bool>("isRoot") ? page.Ancestors(_navLevelCounter).FirstOrDefault()?.Id : page.Id;

        return new NavigationModel
        {
            Text = page.Value<string>("navigationText"),
            MegaMenuImage = page.Value<IPublishedContent>("megaMenuImage")?.Url,
            Link = page.Url,
            UseLink = page.Value<bool>("useLink"),
            Category = Umbraco.GetDictionaryValue(page.Value<string>("navigationCategory")),
            CategoryOrderIndex = page.Value<int>("navigationCategoryOrderIndex"),
            Children = childNavigationModels,
            Id = page.Id,
            RootParentId = rootParentId
        };
    }
}

This worked perfectely for weeks. Suddenly this error came up.

All folders got write permissions for the app pool. So where could be the problem? Can/should I turn off the usage of the cache? How?

I really stuck.

Thank you for your help.

Peter