I think this is explained a little better here http://msdn.microsoft.com/en-us/library/65zzykke.aspx, specially if you look at the middle example.

You can use more than one yield statement in the same iterator as in the following example:

public System.Collections.IEnumerator GetEnumerator()
{
    yield return "With an iterator, ";
    yield return "more than one ";
    yield return "value can be returned";
    yield return ".";
}

You can then print the results using the following foreach statement:

foreach (string element in new TestClass())
{
    System.Console.Write(element);
}
// Output: With an iterator, more than one value can be returned.

This example displays the following text:

With an iterator, more than one value can be returned.

On each successive iteration of the foreach loop (or the direct call to IEnumerator.MoveNext), the next iterator code body
resumes after the previous yield statement and continues to the next until the end of the iterator body is reached,
or a yield break statement is encountered.

Iterators do not support the IEnumerator.Reset method. To re-iterate from the beginning, you must obtain a new iterator.