Custom Ditto ValueResolver - Single IPublishedContent from IEnumerable<IPublishedContent

CustomDittoValueResolver.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using Our.Umbraco.Ditto;
using Umbraco.Core.Models;

namespace My.Website.ComponentModel
{
    public class SinglePublishedContentUmbracoPropertyAttribute : UmbracoPropertyAttribute
    {
    }

    public class SinglePublishedContentValueResolver : UmbracoPropertyValueResolver
    {
        public override object ResolveValue()
        {
            var value = base.ResolveValue();

            if (value is IEnumerable<IPublishedContent>) {
                return (value as IEnumerable<IPublishedContent>).FirstOrDefault();
            }
            throw new InvalidCastException(string.Format("Invalid value resolver! The value must be of type {0}", typeof(IEnumerable<IPublishedContent>)));
        } 
    }
}

Found this while Googleing and didn't have any context. For future Googlers, this is the thread that this code was born from:

https://our.umbraco.org/projects/developer-tools/ditto/ditto-feedback/71581-ienumerableipublishedcontent-to-single-ipublishedcontent-dittovalueresolver-or-typeconverter