Model Binding to Enums in ASP.NET MVC 3

Question

I have a method in my controller that accepts an object as an argument and returns a JsonResult. One of the properties on this object is an enum with three possible values.

Answer 1

Ok guys. I've looked up a few ways to do this because I was tired of writing stupid work around to get past this deficiency in the .Net framework. Based on a couple of threads, I have composed the following solution.

Disclaimer, this is not a totally automated solution, so it will not work for all. Given my implementation, it works. Maybe my way will help someone else design something that will work for them.

First, I created an enum respository. The enums don't have to reside here, but they would need to be visible from the repository.

In the repository, I created a class and a public static property to expose a list of enum types.

namespace MyApp.Enums
{
    public enum ATS_Tabs { TabOne = 0, TabTwo = 1, TabThree = 2, TabFour = 3, TabFive = 4 };

    public class ModelEnums
    {
        public static IEnumerable Types
        {
            get
            {
                List Types = new List();
                Types.Add(typeof(ATS_Tabs));
                return Types;
            }
        }
    }
}

Next, I created a model binder and implemented the IModelBinder interface (ref. kdawg's comment and link).

namespace MyApp.CustomModelBinders
{
    public class EnumModelBinder : IModelBinder
    {
        public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
        {
            ValueProviderResult valueResult = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);
            ModelState modelState = new ModelState { Value = valueResult };
            object actualValue = null;

            try
            {
                return Enum.ToObject(Type.GetType(bindingContext.ModelType.AssemblyQualifiedName), Convert.ToInt32(valueResult.AttemptedValue));
            }
            catch (FormatException e)
            {
                modelState.Errors.Add(e);
            }

            bindingContext.ModelState.Add(bindingContext.ModelName, modelState);
            return actualValue;
        }
    }
}

It might help to add some code to ensure the conversion of valueResult.AttemptedValue doesn't fail.

Next, I looped through the list of enum types I created above and added model binders for them (...in Global.asax.cs).

    protected void Application_Start()
    {
        AreaRegistration.RegisterAllAreas();

        foreach (Type type in ModelEnums.Types)
        {
            ModelBinders.Binders.Add(type, new EnumModelBinder());
        }

        RegisterGlobalFilters(GlobalFilters.Filters);
        RegisterRoutes(RouteTable.Routes);
    }

I admit, this it not the most intuitive way, but it works great for me. Feel free to let me know if I can optimize this.