FourOhFourFinder.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Umbraco.Web.Routing;

namespace Diplo.Core
{
    /// <summary>
    /// Umbraco content finder implementation for 404 pages in multi-lingual sites
    /// Assumes each site has a document type with alias of "PageNotFound" in the root of the site (under home node)
    /// </summary>
    public class FourOhFourFinder : IContentFinder
    {
        /// <summary>
        /// Used to find the correct 404 page when a page cannot be found in Umbraco
        /// </summary>
        /// <param name="contentRequest">The current Umbraco context</param>
        /// <returns>The 404 page</returns>
        public bool TryFindContent(PublishedContentRequest contentRequest)
        {
            //Check request cannot be found
            if (contentRequest.PublishedContent == null)
            {
                var domain = contentRequest.Domain;

                if (domain != null)
                {
                    var home = contentRequest.RoutingContext.UmbracoContext.ContentCache.GetById(domain.RootNodeId);

                    if (home != null)
                    {
                        //Get the 404 node
                        var notFoundNode = home.Children.FirstOrDefault(x => x.DocumentTypeAlias == "PageNotFound");

                        if (notFoundNode != null)
                        {
                            //Set Response Status to be HTTP 404
                            contentRequest.SetResponseStatus(404, "404 Page Not Found");

                            //Set the node to be the not found node
                            contentRequest.PublishedContent = notFoundNode;
                        }
                    }
                }
            }

            return contentRequest.PublishedContent != null;
        }

        /// <summary>
        /// Also need to register the handler in OnApplicationStarting
        /// </summary>
        public void ApplicationStarting(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
        {
            ContentFinderResolver.Current.InsertTypeBefore<ContentFinderByNotFoundHandlers, Diplo.Core.FourOhFourFinder>();
        }
    }
}