A default-constructed instance of the System.Random class. A part of the C# Language Syntactic Sugar suite.
$ dotnet add package CLSS.Constants.DefaultRandomSystem.Random requires a class instance to be used. Constructing a new instance each time you need a random number generator will allocate some memory for that instance. This incurs an allocation cost and a runtime garbage collection cost. .NET developers seemingly have realized this is an issue and added System.Random.Shared in .NET 6, but for many projects still bound to an earlier version of .NET, this shared Random instance is not available.
Once you install this package, you can access a global, persisting System.Random instance with CLSS.DefaultRandom.Instance.