Iterator pattern in the .NET BCL

The iterator pattern is so common that most platforms and frameworks provide a mechanism to support it. The .NET BCL has got IEnumerable and its generic variant , that is, IEnumerable<T> to implement custom iterators. To iterate, we have got the foreach loop construct in C#. Similar constructs are available in Java as well. The following program creates a custom list by leveraging the .NET fixed length array facility:

    public class CustomList<T> : IEnumerable<T> 
    { 
      //------ A Fixed Length array to  
      //------ Example very simple 
      T[] _Items = new T[100]; 
      int next_Index = 0; 
 
      public CustomList(){} 
 
      public void Add(T val) 
      { 
        // We are adding value without robust 
        // error checking 
        _Items[next_Index++] = val; 
      } 
 
      public IEnumerator<T> GetEnumerator() 
      {...