Question

I have a custom model binder that takes a comma separated list and cleans out any empty values, then passes it along to the default model binder. This worked in ASP.NET MVC Preview 2, but when I upgraded to RC2, the below won’t compile because the interface of ValueProvider only has a GetValue() method, no [] accessor. Is what I’m doing below possible through some other mechanism in the binding context? I’d rather not have to create a full blown model binder for such a simple situation. The main goal is when the values are bound to a List<SomeEnum>, any empty values are skipped.

public class EnumListModelBinder : IModelBinder
{
    public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        var result = bindingContext.ValueProvider[bindingContext.ModelName];
        string[] rawValues = (string[])result.RawValue;
        var newValues = new List<string>();
        foreach (string value in rawValues)
        {
            if (!String.IsNullOrEmpty(value))
            {
                newValues.Add(value);
            }
        }

        string newValuesAttempted = String.Join(",", newValues.ToArray());
        // overwrite the ValueProviderResult with the cleaned up csv list
        // this is the part I'm not sure how to implement using the interface
        bindingContext.ValueProvider[bindingContext.ModelName] = 
           new ValueProviderResult(newValues.ToArray(), newValuesAttempted, result.Culture);

        return System.Web.Mvc.ModelBinders.Binders.DefaultBinder.BindModel(controllerContext, bindingContext);
    }
}

Answer 1

There wasn’t much of a solution here now that the ValueProvider collection is readonly. Instead I ended up using a custom model binder

Is there a way to have the DefaultModelBinder ignore empty items when binding to a List<Enum>