Rider Help

Using Annotations to Refine Code Inspection

Code inspection and many other Rider features largely rely on knowing behavior of language constructs to detect issues, suggest possible improvements, and help you in other ways.

However, this kind of analysis cannot detect everything. For example, if a method is designed to never return null and its clients are designed accordingly, no structural analysis will find a possible issue if someone has changed the method to return null.

In this and a lot of other cases, the Rider's JetBrains.Annotations is of a great help. By using attributes declared in this framework you can make Rider analyze code the way you need it. For example:

[NotNull] public object Foo() { return null; // Warning: Possible 'null' assignment }

This being the simplest example, there are other helpful attributes with more complex use cases. You can find the full list of these attributes in the reference.

In most cases, code annotation attributes enable specific code inspections, for example:

Also, code annotations enable more quick-fixes, code completion suggestions, and code generation features on annotated items. The annotations are also required to create and use Source Templates.

Rider allows you to annotate code symbols in two ways:

  • You can annotate symbols in your source code as shown in the example above. In this case, you need to reference JetBrains.Annotations namespace in your project. For more information, see Annotations in Source Code.
  • Even if you do not have access to sources, you can annotate symbols in compiled library code. For more information, see External Annotations.
Last modified: 11 October 2017

See Also