April 2009 - breath of fresh marasm

In general I think that EPiServer code is a little bit too sealed. I hate all those classes where you can not reimplement part of the code on your own or where you can not overwrite methods. However, this time I was nicely surprised. It was enough to create custom implementation of the EPiServer.PlugIn.PlugInAttribute and use DataFactory.Instance.FinishedLoadingChildren event.

Actually, on the beginning I wanted to use DataFactory.Instance.LoadingChildren and set RequiredAccess to AccessLevel.Edit (see below), but it didn't work for me. If you know why, please comment so I can learn something :)

private static void Instance_LoadingChildren(object sender, ChildrenEventArgs e)
{
    e.RequiredAccess = AccessLevel.Edit;
}

First I created my class inheriting from EPiServer.PlugIn.PlugInAttribute and implemented Start method so it adds new ChildrenEventHandler to the DataFactory.Instance.FinishedLoadingChildren event:

using System.Web;
using EPiServer;
using EPiServer.Configuration;
using EPiServer.Core;
using EPiServer.PlugIn;
using EPiServer.Security;

namespace Maras.TreeAdapter
{
    public class TreeAdapter : PlugInAttribute
    {
        public static void Start()
        {
            DataFactory.Instance.FinishedLoadingChildren += Instance_FinishedLoadingChildren;
        }

        private static void Instance_FinishedLoadingChildren(object sender, ChildrenEventArgs e)
        {
            if (IsAccessCheckNecessary(e))
            {
                int index = 0;
                while (index < e.Children.Count)
                {
                    if (e.Children[index].ACL.HasAccess(PrincipalInfo.Current.Principal, AccessLevel.Edit))
                    {
                        index++;
                    }
                    else
                    {
                        e.Children.RemoveAt(index);
                    }
                }
            }
        }
    }
}

As you can see, I check whether the access control is necessary and then I remove all the children that current user is not allowed to edit. Pretty important is the IsAccessCheckNecessary method. My implementation assumes that I want to filter pages in edit mode and for the children of the start page only, so it looks like this:

private static readonly string UI_URL = Settings.Instance.UIUrl.ToString().ToLower();

private static bool IsAccessCheckNecessary(ChildrenEventArgs e)
{
    return e.PageLink == PageReference.StartPage &&
           HttpContext.Current.Request.Url.ToString().ToLower().StartsWith(UI_URL);
}

If you know any easier way of doing what I needed, feel free to comment below.

Source code can be downloaded from here: source code