Question

I successfully made Enum binder and from what iv tested, everything works. But i want to have nullable enum parameter in my controller and when i change to nullable, my binder dont work.

 public class EnumBinder<T> : IModelBinder
    {
        private object DefaultValue { get; set; }
        public EnumBinder(object defaultValue)
        {
            DefaultValue = defaultValue;
        }


        public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
        {
            var result = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);

            if(result == null || string.IsNullOrEmpty(result.AttemptedValue))
            {
                return DefaultValue;
            }

            return GetEnumValue<T>(result.AttemptedValue);
        }



        public static object GetEnumValue<T>(string value)
        {
            var enums = Enum.GetValues(typeof (T)).Cast<T>().ToList();

            foreach (var e in enums)
            {
                var _enum = Enum.Parse(typeof (T), e.ToString());
                if (string.Equals(value, _enum.ToString(), StringComparison.InvariantCultureIgnoreCase))
                {
                    return _enum;
                }
            }

            return null;
        }

    }

Works on

 public virtual ActionResult ControllerName(Status status)
    {
       return View();
    }

but dont work on

 public virtual ActionResult ControllerName(Status? status)
    {
       return View();
    }

Of course i have registered my binder on application start

ModelBinders.Binders.Add(typeof(CallStatus), new EnumBinder<CallStatus>(null));

What i do wrong, why i cant return nullable enum in my controller?

Answer 1

CallStatus and CallStatus? are different types. The ? is syntactic sugar; CallStatus? is actually type System.Nullable<CallStatus>.

You need to either add another binder for typeof(Nullable<CallStatus>), or use a provider, as described here.