Those who are familiar with BizTalk 2006, should know about Development and Deployment modes in Visual Studio. Personally, I never questioned why it's not Debug and Release just like everything else in Visual Studio. Then everything changed in BizTalk 2010. BizTalk and Visual Studio 2010 now uses Debug and Release modes by default. When we upgraded BizTalk 2006 solution to 2010, Development and Deployment modes remained unchanged for all the projects, and code compiled without any issues. Soon, I realized that any new projects added to the converted solutions started using Debug and Release modes. This also didn't cause any problem compiling the solution from Visual Studio; however, it broke our custom build/deployment scripts since the scripts were trying to build in Deployment mode. So, I decided to change all projects from Development and Deployment modes to Debug and Release modes to keep them consistent. During this process I realized that Debug and Release modes are defaults; but it's completely customizable. During the BizTalk 2010 upgrade process, I figured that switching to default Debug and Release modes are the best options.