K2 workflow definitions use what we call the extender projects behind the scene. These code behinds allow us to work at the .XOML and .CS layers. In 807 you may be surprised to see these projects missing in the VS.NET solution explorer.
This is by design and actually the projects are there but they are hidden from view. The location where these files get generated is also changed. Since these files are generated by K2 during design time and worked on by the developer, they dont need to be checked-in to your source control systems. The .kprx file stores all the information and code related to the process definition. So, it is better to keep and treat these files as TEMP. So, in 807 these files are generated in the %TEMP% folder of your windows session.
Typically %TEMP% is the TEMP directory in your my documents folder. There is a catch with this. If you happen to use very long names for your K2 activities and events you will find that the extender code files generated will encounter the file path name restriction of 256 characters imposed by windows. So, it is best to set this %TEMP% location to some writable folder in the root directory of your system.
If you are upgrading from 803 or SP1 to 807, please note that you need to update your event templates in the .kprx files to experience the improved performance in VS.NET. This is to do with changes in the underlying project system with 807.
On another note, there is a permission requirement introduced in 807. If you are using ProcessInstance.update() calls instead of the new actions and outcomes framework’s update action mechanism, you will need to grant ‘admin’ permission for the user who is executing the processinstance.update() call. UPDATE: Read this KB article.
and this KB article on registering custom security providers.