logic behind upgrading web applications in asp.net?

I have been trying to figure out the logic of upgradi开发者_如何学Pythonng web applications. Like in case of DNN. It provides upgrades to switch to newer versions. How is the existing data managed? Do we replace the whole project :P? What goes behind the scenes?

Thanks

It really depends what has been modified between versions.

• Entirely new data structures can be added and left empty
• Any changes to existing data structure must either:
  • Have default values
  • Have some way to automatically convert/populate from existing values
  • Prompt the user if necessary. (Last resort option)

Once the upgraded data structure is in place, the corresponding web site code can be deployed. In most cases, the code will only work with the corresponding data structure version. And, normally, the code updates can be deployed using either "delete existing" or "full overwrite".