AllowNullAttribute
Specifies that null is allowed as an input even if the corresponding type disallows it.
namespace System.Diagnostics.CodeAnalysis
{
[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Parameter, Inherited = false)]
[ExcludeFromCodeCoverage]
internal sealed class AllowNullAttribute : Attribute
{
}
}