Don't define NRT attrs unless net4xx/netstandard2.0
+#if NETFRAMEWORK || NETSTANDARD2_0
namespace System.Diagnostics.CodeAnalysis {
[AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
sealed class NotNullWhenAttribute : Attribute {
@@ -9,3 +10,4 @@ namespace System.Diagnostics.CodeAnalysis {
public DoesNotReturnAttribute() { }
}
}
+#endif
