The most popular feature of
JetBrains.Annotations is probably the addition of two cool attributes: [NotNull] and [CanBeNull]. They add a meta-information to a marked element, describing if
null is a correct value for that element, or not. Then, developers using ReSharper would get help from the IDE and could easier avoid mistakes like here:
I discovered them a few years ago when they were extensively used in a project I also worked on. At that time, there was no native support for anything similar in C#. I remember some of us always used it, and some of it avoided it and were against introducing some 3rd party library and attributes just to get some new warnings in the IDE. I have seen a high value in it. It became a standard part of my toolkit ever since.
Luckily, since C#8 we can mark types as non-nullable natively. We don’t need ReSharper or attributes from their library.
So, is there an easy, automated way, to migrate from
[CanBeNull] usages to the modern Nullable Reference Types? Yes! But if you don’t want to replace each usage individually in the code editor, things needs to be done in the right order.
How to migrate solution using Visual Studio
I assume you start with a project that uses annotations, like here:
- Don’t remove reference to the
Jetbrains.Annotationspackage yet! It’s needed for the automated refactoring to work.
- Enable Nullable Reference types in the project by adding
*.csprojfile, or enable it in the Visual Studio’s UI.
- Use the refactoring named “Use type annotation syntax”, as depicted in a screenshot. You can choose the scope of a whole project or solution.
- Now you can remove the reference to
JetBrains.Annotationspackage. Check if the project still compiles. Your project might have usages of other, less popular attributes from the package that might or might not have a replacement in native C# or .NET features at this point – fix them individually.
I hope it helps you save some time 🙂