Reports diagnostics, helping you to annotate your source tree with (Item)NotNull / (Item)CanBeNull attributes. See also: https://www.jetbrains.com/resharper/help/Code_Analysis__Code_Annotations.html You need Visual Studio 2013/2012/2010 and Resharper v8 or higher to use this analyzer. See package "ResharperCodeContractNullability" if you use Visual Studio 2015.
$ dotnet add package ResharperCodeContractNullabilityFxCopNo README available.