Venkat,
There are no points for awarded for the most posts not relevant to the question. And there is no reason to reply to every post on the forum with with quotes.
You did see that my post was related to "Java" right? Replying with a link to 9.2 .NET documentation really doesn't serve a purpose, especially when the example link I posted was a 10.0 Java sample using a GeometryBag.
The point I was trying to make was that the docs indicated that constructUnion() does not work with GeometryBags, yet the sample showed a GeometryBag being cast to IEnumGeometry as a parameter to constructUnion().