namespace System.Diagnostics.CodeAnalysis { [AttributeUsage(AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Parameter, Inherited = false)] internal sealed class DisallowNullAttribute : Attribute { } } namespace System.Diagnostics.CodeAnalysis { [AttributeUsage(AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.ReturnValue, Inherited = false)] internal sealed class MaybeNullAttribute : Attribute { } }