Hi,
I would look at http://www.microsoft.com/learning/en/us/exam.aspx?ID=70-536&locale=en-us#tab2 for the requirements and look at the associated learning plan. Whether it is mandatory depends on the company that you work for or whether the class that you
are taking requires passing the exam. If you want to get the MCPD ( http://www.microsoft.com/learning/en/us/certification/mcpd.aspx#tab2 ), it would seem that it is required.
-- Mike Burr