MemberNotNullAttribute
namespace System.Diagnostics.CodeAnalysis
{
    [AttributeUsage(AttributeTargets.Method | AttributeTargets.Property, Inherited = false, AllowMultiple = true)]
    internal sealed class MemberNotNullAttribute : Attribute
    {
        public string[] Members { get; }
        public MemberNotNullAttribute(string member)
        {
            Members = new string[1] {
                member
            };
        }
        public MemberNotNullAttribute(params string[] members)
        {
            Members = members;
        }
    }
}