This question is similar to https://world.episerver.com/forum/developer-forum/-Episerver-75-CMS/Thread-Container/2021/2/multiple-string-values-in-custom-visitor-group-criterion/ (and funny it was posted just before I posted this), but in my case I'm creating a Criterion for selecting Episerver User Groups / Roles and I have two problems:

1. What property type should the model have ("Groups" below)?
2. How do I display a list of labeled checkboxes in the UI, i.e is there a DojoWidget that works? I am currently using MultiSelect and it displays the items fine, but I would prefer something like the weekday editor in the TimeOfDay criterion, i.e similar to the SelectMany attribute

With the setup below, I get a "Failed to convert item" error when I try to save it in episerver:

	public class UserGroupsCriterionModel : CriterionModelBase
	{
		[DojoWidget(WidgetType = "dijit.form.MultiSelect", SelectionFactoryType = typeof(UserGroupSelectionFactory))]
		public string[] Groups { get; set; }

		public override ICriterionModel Copy()
		{
			return base.ShallowCopy();
		}
	}

	public class UserGroupSelectionFactory : EPiServer.Personalization.VisitorGroups.ISelectionFactory
	{
		public IEnumerable<SelectListItem> GetSelectListItems(Type propertyType)
		{
			return System.Web.Security.Roles.GetAllRoles().Select(t => new SelectListItem { Text = t, Value = t });
		}
	}

	[VisitorGroupCriterion(Category = "Custom", Description = "", DisplayName = "User Groups")]
	public class UserGroupsCriterion : CriterionBase<UserGroupsCriterionModel>
	{
		public override bool IsMatch(IPrincipal principal, HttpContextBase httpContext)
		{
			return httpContext.User.Identity.IsAuthenticated && Model.Groups.Intersect(System.Web.Security.Roles.GetRolesForUser(httpContext.User.Identity.Name)).Any();
		}
	}