Enumerators and Iterators - Illustrated C# 2005 - page 468

The Generic Enumeration Interfaces
The third form of the enumerator uses the generic interfaces IEnumerable<T> and IEnumerator<T> .
They are called generic because they use C# generics. Using them is very similar to using the non-
generic forms. Essentially, the differences between the two are the following:

￿ With the non-generic interface form

-The GetEnumerator method of interface IEnumerable returns an enumerator class
instance that implements IEnumerator .

The class implementing IEnumerator implements property Current , which returns
an object .

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￿ With the generic interface form

-The GetEnumerator method of interface IEnumerable<T> returns an enumerator class
instance that implements IEnumerator<T> .

The class implementing IEnumerator<T> implements property Current , which returns
a derived type.

-

Notice that, with the generic interfaces , the items you receive from the enumeration are a
specific derived type, whereas with the non-generic interfaces, you get back the more “generic”
object from the enumerations.