NULL reference exception while reading user sessions (Reflection)

Question

I have implemented the code for reading the active sessions using the reference Reading All Users Session and Get a list of all active sessions in ASP.NET.

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Answer 1

I've tried Paully's solution, which didn't compile in some points and lead to runtime errors in others. Anyway, inspired on his suggestion (thanks a lot! My vote goes for that), I came to my own, which compiles and gets me the expected data.

Also, I'm returning a IEnumerable and I'm using "yield return", which makes it more performatic for big lists (kind of lazy loading of data). Here it goes:

public static System.Collections.Generic.IEnumerable GetAllUserSessions()
{
    List hTables = new List();
    object obj = typeof(HttpRuntime).GetProperty("CacheInternal", BindingFlags.NonPublic | BindingFlags.Static).GetValue(null, null);
    dynamic fieldInfo = obj.GetType().GetField("_caches", BindingFlags.NonPublic | BindingFlags.Instance);

    //If server uses "_caches" to store session info
    if (fieldInfo != null)
    {
        object[] _caches = (object[])fieldInfo.GetValue(obj);
        for (int i = 0; i <= _caches.Length - 1; i++)
        {
            Hashtable hTable = (Hashtable)_caches[i].GetType().GetField("_entries", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(_caches[i]);
            hTables.Add(hTable);
        }
    }
    //If server uses "_cachesRefs" to store session info
    else
    {
        fieldInfo = obj.GetType().GetField("_cachesRefs", BindingFlags.NonPublic | BindingFlags.Instance);
        object[] cacheRefs = fieldInfo.GetValue(obj);
        for (int i = 0; i <= cacheRefs.Length - 1; i++)
        {
            var target = cacheRefs[i].GetType().GetProperty("Target").GetValue(cacheRefs[i], null);
            Hashtable hTable = (Hashtable)target.GetType().GetField("_entries", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(target);
            hTables.Add(hTable);
        }
    }

    foreach (Hashtable hTable in hTables)
    {
        foreach (DictionaryEntry entry in hTable)
        {
            object o1 = entry.Value.GetType().GetProperty("Value", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(entry.Value, null);
            if (o1.GetType().ToString() == "System.Web.SessionState.InProcSessionState")
            {
                SessionStateItemCollection sess = (SessionStateItemCollection)o1.GetType().GetField("_sessionItems", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(o1);
                if (sess != null)
                     yield return sess;
            }
        }
    }
}