Allow Nullables in Attributes

[TonyValenti]

Hi! I want to be able to have nullable parameters on my attributes but it is not allowed.

    [AttributeUsage(AttributeTargets.Class, AllowMultiple =false)]
    public class StartupExtensionOptionsAttribute : Attribute {
        public bool InitializeRequired { get; private set; }
        public long InitializePriority { get; private set; }

        public bool StartupRequired { get; private set; }
        public long StartupPriority { get; private set; }

        
        public long ShutdownPriority { get; private set; }

        public StartupExtensionOptionsAttribute(bool StartupRequired = false, long StartupPriority = 0, bool? InitializeRequired = null, long? InitializePriorty = null, long? ShutdownPriority = null)  {
            this.StartupRequired = StartupRequired;
            this.StartupPriority = StartupPriority;

            this.InitializeRequired = InitializeRequired ?? StartupRequired;
            this.InitializePriority = InitializePriorty ?? StartupPriority;

            this.ShutdownPriority = ShutdownPriority ?? -StartupPriority;
        }

    }

[HaloFour]

The limitation on the types allowed to be embedded in attribute metadata comes from the CLR and there isn't much that the compiler can do to overcome it directly. As such you might want to take up the request there.

However, since C# 1.0 there has been a different pattern for using optional values in attributes and that has been named properties. Why is this not sufficient here?

    [AttributeUsage(AttributeTargets.Class, AllowMultiple =false)]
    public class StartupExtensionOptionsAttribute : Attribute {
        private bool? _intializeRequired;
        private long? _intializePriority;
        private long? _shutdownPriority;

        public bool StartupRequired { get; private set; }
        public long StartupPriority { get; private set; }

        public bool InitializeRequired {
            get => _initializeRequired ?? StartupRequired;
            set => _initializeRequired = value;
        }

        public long InitializePriority {
            get => _initializePriority ?? StartupPriority;
            set => _initializePriority = value;
        }

        public long ShutdownPriority {
            get => _shutdownPriority ?? -StartupPriority;
            set => _shutdownPriority = value;
        }

        public StartupExtensionOptionsAttribute(bool startupRequired, long startupPriority) {
            StartupRequired = startupRequired;
            StartupPriority = startupPriority;
        }
    }

// usage:

[StartupExtensionOptions(true, 100, InitializeRequired = true)]

[jnm2]

Is this included in the request for constructed generic types to be used as attribute arguments?