Dynamic Page Type Selector

GlobalPage.cs

    [ContentType(
        DisplayName = "Global Search",
        GUID = "1B83AF7C-BC4B-4A13-8AAB-B9313D25D284",
        GroupName = Global.PageGroups.Content,
        Description = "")]
    public class GlobalSearchPage : SitePageBase, IAllowedPageType
    {
        [Display(
            Name = "Page Types",
            GroupName = SystemTabNames.Content,
            Order = 10)]
        [SelectMany(SelectionFactoryType = typeof(SearchPageTypeSelectionFactory))]
        public virtual string PageTypes { get; set; }
    }

InterfaceHelper.cs

    public class InterfaceHelper
    {
        public static IEnumerable<Type> GetAllTypes<TInterface>()
        {
            return AppDomain.CurrentDomain
                    .GetAssemblies()
                    .SelectMany(x => x.GetTypes())
                    .Where(x => typeof(TInterface).IsAssignableFrom(x) && !x.IsInterface && !x.IsAbstract && !x.Name.Contains("Proxy"));
        }
    }

SearchPageTypeSelectionFactory.cs

    public class SearchPageTypeSelectionFactory : ISelectionFactory
    {
        private static IEnumerable<Type> Posts => InterfaceHelper.GetAllTypes<IPostSearch>();

        private static IEnumerable<Type> Pages => InterfaceHelper.GetAllTypes<IPageSearch>();

        public IEnumerable<ISelectItem> GetSelections(ExtendedMetadata metadata)
        {
            var types = Posts.Union(Pages);
            return types.Select(t => new SelectItem { Text = t.Name.ToProperCase(), Value = t });
        }
    }

StringExt.cs

    public static class StringExtensions
    {
       // Capitalize the first character and add a space before each capitalized letter (except the first character).
        public static string ToProperCase(this string strText)
        {
            // If there are 0 or 1 characters, just return the string.
            if (strText == null) return strText;

            if (strText.Length < 2) return strText.ToUpper();

            // Start with the first character.
            var result = strText.Substring(0, 1).ToUpper();

            // Add the remaining characters.
            for (var i = 1; i < strText.Length; i++)
            {
                if (char.IsUpper(strText[i])) result += " ";

                result += strText[i];
            }

            return result;
        }
    }
}