ReSharper 2017.1 Help

Annotations in Source Code

The easiest way to benefit from ReSharper's code annotations is to add the annotation attributes to symbols of your source code and make ReSharper analyze your solution with greater accuracy and insight.

By default, all annotation attribute classes are marked with [Conditional("JETBRAINS_ANNOTATIONS")] so the compiler will ignore the attribute usages in your code, which means that no binary reference to the 'JetBrains.Annotations.dll' assembly will be produced. However, you can define 'JETBRAINS_ANNOTATIONS' conditional compilation symbol in your projects to preserve the attributes in metadata.

In this topic:

Enabling ReSharper code annotations support in your project

To make use of ReSharper code annotation attributes in your project, you should reference them in one of the following ways:

  • The recommended way is to install the NuGet package with the JetBrains.Annotations assembly.
    Actually, you do not even need to go to the NuGet website to get the package. Just add the using JetBrains.Annotations; directive, and use the corresponding context action to automatically fetch the package.
    A quick-fix that automatically fetches JetBrains.Annotations package from NuGet
  • You can simply add a project reference to the JetBrains.Annotations.dll, which you can find in the ReSharper installation directory..
  • You can also insert attribute declarations anywhere in your project. If necessary, you can insert them into other namespace.
    You can copy the declarations on the Code Inspection | Code Annotations page of ReSharper options. Optionally, you can choose to make the declarations internal and/or add the [Conditional("JETBRAINS_ANNOTATIONS")] attribute to the declarations.

If the JetBrains.Annotations.dll is referenced or attribute declarations are inserted in any of the projects within your solution, you can type the desired annotation attribute and press Alt+Enter to invoke the quick-fix that will reference this module in the current project and add the missing namespace import directive:

Quick-fix for adding reference to the JetBrains.Annotations module

Alternatively, you can press Ctrl+Alt+Space twice to invoke the double import completion, which will find the attribute, import the namespace, and add the reference.

Importing the NotNull attribute with code completion

The default implementation of the annotation attributes is inserted in the JetBrains.Annotations namespace, but this namespace is not required for the correct functioning of the annotations. You can put these classes anywhere in your solution - ReSharper will detect them automatically. However, if you chose to do so, you should select the proper namespace by following the procedure below.

There may be cases when your solution contains several implementations of the annotation attributes, e.g., you have classes with the same names as ReSharper annotations classes (CanBeNullAttribute, NotNullAttribute, etc.) or you are using a third-party assembly that contains ReSharper annotation classes. In such cases, you can choose the namespace where ReSharper should look for the proper set of annotation attribute classes.

To manage ReSharper code annotations sources

  1. Open the Code Inspection | Code Annotations page of ReSharper options.
  2. All namespaces (from both source code and references assemblies) other than JetBrains.Annotations with the annotation classes are shown in the Namespaces with code annotation attributes list. Check the entries that contain the desired implementation.
  3. If there are several namespaces in the list, select the one that should be used by the ReSharper code analysis engine it in the Default annotation namespace drop-down list.
  4. Click Save to apply the modifications and let ReSharper choose where to save them, or save the modifications to a specific settings layer using the Save To drop-down list. For more information, see Managing and Sharing ReSharper Settings.

Using Context Actions to add annotation attributes

As soon as ReSharper is aware of annotation classes location, you can use context actions to add the most popular annotation attributes:

  • [NotNull]
  • [CanBeNull]
  • [UsedImplicitly]

To add these annotations, press Alt+Enter on the symbol you want to annotate, and ReSharper will suggest an attribute depending on the context:

Last modified: 12 October 2017

See Also