Upgrade to CMS 10

No data migration is required; updating to Optimizely Content Management System (CMS 10) is no different from updating to the feature updates delivered previously via NuGet. To make sure the upgrade is as smooth as possible, there are a few steps that you may want to take that are discussed in the next sections.

Breaking changes, what are they, and how to deal with them

A breaking change is a change that might cause other components to fail. When a breaking change is done to the signature of a method/class/interface, the old signature is often kept intact but set as obsolete and may cause a warning message in Visual Studio. As long as the Visual Studio project setting "Treat Warnings as Errors" is not enabled in Visual Studio, you can postpone fixing these warnings until later.

Classes that expose constructors that take dependencies are normally deleted without an obsolete warning in major releases because the compiler gives enough information about what to change. Keeping them makes dependency injection complex because there are multiple constructors to choose from that, over time, might or might not overlap.

Obsolete methods are removed permanently in each major version to keep the API clean and usable over time. So, even if you can postpone fixing warning messages, ensuring they are fixed before upgrading to a major version is good practice. For CMS 10, many methods made obsolete in 9.0 are now deleted.

Find the complete list of breaking changes for CMS 10 here.

Add-ons managed with Visual Studio can be upgraded with the platform through NuGet. Add-ons that are installed via the user interface have to be upgraded through the user interface.

You should install add-ons through the user interface and convert them to NuGet add-ons after the upgrade to CMS 10. A tool can automatically convert add-ons previously managed through the user interface to be managed as NuGet packages with Visual Studio. For instructions on converting user interface add-ons to NuGet add-ons, see Linus Ekström's blog post Upgrading your site and add-ons to EPiServer CMS 8 pre-release.

Incompatible add-ons installed through the user interface must be disabled to reach the user interface and the update functionality. An exception message is shown with information on how to disable an add-on that blocks startup.