There is an error under the section Remarks in paragraph 1.
It is not possible to update the elements in a collection by updating the element that is returned by the for each command. The for each command returns an object by value, not by reference.
The for each command reference explains this:
http://msdn.microsoft.com/en-us/library/ttw7t8t6(VS.80).aspx
The foreach statement is used to iterate through the collection to get the desired information, but should not be used to change the contents of the collection to avoid unpredictable side effects.