Custom ModelBinder not working for Nullable types

Question

I have the following custom ModelBinder for DateTime:

public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        ValueProviderResult value = null;
        try
        {
            value = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);
            return DateTime.ParseExact(value.AttemptedValue, _customFormat, CultureInfo.InvariantCulture);
        }
        catch (Exception)
        {
            // If there is a place where DateTime got used which "Bypassed" our EditorTemplate, it means the format will be the default format.
            // So let's allow the Model Binder to at least try to Parse the date with the default format.
            return DateTime.Parse(value.AttemptedValue);
        }
    }

If I specify the argument in my Action as a nullable DateTime ( DateTime? dob ), the ModelBinder does not fire.

How can I make the ModelBinder work for nullable DateTime?

Answer 1

You need to register it twice, like this:

ModelBinders.Binders.Add(typeof (DateTime), new DateTimeModelBinder());
ModelBinders.Binders.Add(typeof (DateTime?), new DateTimeModelBinder());