Provides static classes for representing program contracts such as preconditions, postconditions, and invariants. Commonly Used Types: System.Diagnostics.Contracts.Contract System.Diagnostics.Contracts.ContractClassAttribute System.Diagnostics.Contracts.ContractClassForAttribute System.Diagnostics.Contracts.ContractFailureKind System.Runtime.CompilerServices.ContractHelper System.Diagnostics.Contracts.ContractInvariantMethodAttribute System.Diagnostics.Contracts.PureAttribute System.Diagnostics.Contracts.ContractArgumentValidatorAttribute System.Diagnostics.Contracts.ContractVerificationAttribute System.Diagnostics.Contracts.ContractOptionAttribute When using NuGet 3.x this package requires at least version 3.4.