System.Collections.Generic.IEnumerable<T> is the base interface for collections in the System.Collections.Generic namespace such as List<T>
Dictionary<TKey,TValue>
Stack<T> IEnumerable<T> include ObservableCollection<T> and
ConcurrentStack<T>. IEnumerable<T> (the other subset operates on IQueryable<T>). IEnumerable<T> implements System.Collections.IEnumerable. System.Linq.Enumerable provides functionality that uses and enhances that if IEnumerable<T>. yield keyword in C#.