we can add or delete in ienumerable but in ienumerable internally returns ienumerator only why ienumerable allows collection modify

Hi,

First of all IEnumerable and IEnumerator are both interfaces. You can think of IEnumerable as a container which contains one method which returns you IEnumeator type of object.

Second, when you are creating your own custom collection class on which you want to iterate then you must derive from IEnumerable to support Iteration over that collection class.

And further you can write the GetEnumerator method in your collection class which returns you IEnumerator object which helps you or provide basic info.

like 1) what is current object which iterating over the collection, 2) MoveNext() method -- are there more elements in collection for iteration??, 3) And Reset() -- resets the iterator pointer.

Hope this helps!