Ok I have a basic data structure as queue and it expose two methods –
add and remove , I have to implement a stack, how can we do that ?

Thanks.

Take a look at the built-in Stack<T>, http://msdn2.microsoft.com/en-us/library/3278tedw.aspx. You can always examine the source code for ideas using Reflector. A simple implementation would be a List or an Array that new articles are added to the end and retrieval fetches the last item.

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Joe (Microsoft MVP - XML)