Non-Generic Vs. Generic Type

Non-Generic	Similar Generic Type
ArrayList	List<T>
Hashtable	Dictionary<TKey,TValue>
SortedList	SortedList<TKey,TValue>
Queue	Queue<T>
Stack	Stack<T>
Ienumerable	IEnumerable<T>
ICollection	N/A (use IEnumerable<T>anything that extends it)
N/A	ICollection<T>
Ilist	IList<T>
CollectionBase	Collection<T>
ReadOnlyCollectionBase	ReadOnlyCollection<T>
DictionaryBase	N/A (just implement IDictionary<TKey,TValue>
N/A	SortedDictionary<TKey,TValue>
N/A	KeyedCollection<TKey,TItem>
N/A	LinkedList<T>

ASP.NET Impersonation

It is an important security feature which have ability to control the identity under which code is executed. Impersonation is when ASP.NET executes code in the context of an authenticated and authorized client. By default, ASP.NET does not use impersonation and instead executes all code using the same user account as the ASP.NET process, which is typically the ASPNET account. This is contrary to the default behavior of ASP, which uses impersonation by default. In Internet Information Services (IIS) 6, the default identity is the NetworkService account.
Impersonation is disabled. This is the default setting. <identity impersonate="false">
Impersonation enabled. In this instance, ASP.NET impersonates the token passed to it by IIS, which is either an authenticated user or the anonymous Internet user account (IUSR_machinename). <identity impersonate="true">
Impersonation enabled for a specific identity. In this instance, ASP.NET impersonates the token generated using an identity specified in the Web.config file. <identity  password="password" impersonate="true" username="domain\user">