Argumentv1.4.0

Argument validation methods, for example: this.user = Argument.NotNull("user", user). Less fancy than approaches based on lambdas/anonymous classes, but less scary performance-wise (given that argument checks are often all over the place). Annotations: C# 8 nullable reference types, ReSharper, Microsoft.CodeQuality.Analyzers, Code Contracts (.NET 4.5 only).