If you are writing .NET applications chances are that it could be the next big LOB application in your organization. Securing those applications could be a problem without an objective methodology. SDL-LOB provides a framework for securing Line Of Business (LOB) applications over lays on top of your standard SDLC phases. It defines certain activities for each phase of SDLC. You can get more information about that at http://msdn.microsoft.com/en-us/library/dd831975.aspx.
Good blog entry by my colleague Anmol on getting familiar with SDL-LOB. Keep following www.msinfosec.com for more updates on SDL-LOB.