Conditional pages for Umbraco Forms

UmbracoFormsExtensionsController.cs

using System;
using System.Collections.Generic;
using System.Linq;
using Umbraco.Forms.Core;
using Umbraco.Forms.Mvc.Models;
using Umbraco.Forms.Web.Controllers;

namespace UmbForms.Extensions
{
    public class UmbracoFormsExtController : UmbracoFormsController
    {
        protected override void OnFormHandled(Form form, FormViewModel model)
        {
            var fieldValues = model.FormState.ToDictionary(kvp => new Guid(kvp.Key), kvp => String.Join(",", kvp.Value));

            while (
                    model.CurrentPage != null &&
                    GetCurrentFields(model).Any() &&
                    (
                        NoFieldsetsShown(form, model, fieldValues) ||
                        NoFieldsShown(form, model, fieldValues)
                    )
                )
            {
                if (
                    (
                        !string.IsNullOrEmpty(Request["__prev"]) ||
                        !string.IsNullOrEmpty(Request["PreviousClicked"])
                    ) && 
                    model.FormStep > 0
                )
                {
                    model.FormStep--;
                    if (model.FormStep < 0)
                        model.FormStep = 0;
                }
                else
                {
                    if (ModelState.IsValid)
                        GoForward(form, model, model.FormState);
                }
            }
        }

        private bool NoFieldsetsShown(Form form, FormViewModel model, Dictionary<Guid, string> fieldValues)
        {
            return CurrentFieldsetConditions(model).All(c => c != null && c.Enabled && !c.IsVisible(form, fieldValues));
        }

        private IEnumerable<FieldCondition> CurrentFieldsetConditions(FormViewModel model)
        {
            return model.CurrentPage.Fieldsets.Select(fs => fs.Condition);
        }

        private static bool NoFieldsShown(Form form, FormViewModel model, Dictionary<Guid, string> fieldValues)
        {
            return CurrentFieldConditions(model).All(c => c != null && c.Enabled && !c.IsVisible(form, fieldValues));
        }

        private static IEnumerable<FieldCondition> CurrentFieldConditions(FormViewModel model)
        {
            return GetCurrentFields(model).Select(f => f.Condition);
        }

        private static IEnumerable<FieldViewModel> GetCurrentFields(FormViewModel model)
        {
            return model.CurrentPage
                .Fieldsets
                .SelectMany(fs => fs.Containers)
                .SelectMany(c => c.Fields);
        }
    }
}