#if !NETCORE #nullable enable namespace System.Diagnostics.CodeAnalysis { [AttributeUsage(AttributeTargets.Property | AttributeTargets.Parameter | AttributeTargets.ReturnValue, AllowMultiple = true)] internal sealed class NotNullIfNotNullAttribute : Attribute { public string ParameterName { get; } public NotNullIfNotNullAttribute(string parameterName) { ParameterName = parameterName; } } } #endif