Extending the UmbracoHelper in Umbraco v8

ISiteService.cs

using Umbraco.Web.PublishedModels;

namespace MyWebSite.Custom
{
    public interface ISiteService
    {
        Website GetWebsite(int id);
        SearchPage GetSearchPage(int id);
    }
}

ModelsBuilder.config

<add key="Umbraco.ModelsBuilder.Enable" value="true" />
<add key="Umbraco.ModelsBuilder.ModelsMode" value="LiveAppData" />
<add key="Umbraco.ModelsBuilder.ModelsDirectory" value="~/Models.Generated" />

RegisterSiteServiceComposer.cs

using Umbraco.Core.Composing;
using Umbraco.Core;

namespace MyWebSite.Custom
{
    [RuntimeLevel(MinLevel = RuntimeLevel.Run)]
    public class RegisterSiteServiceComposer : IUserComposer
    {
        public void Compose(Composition composition)
        {
            composition.Register<ISiteService, SiteService>();
        }
    }
}

SiteService.cs

using System.Linq;
using Umbraco.Core.Models.PublishedContent;
using Umbraco.Web;
using Umbraco.Web.PublishedModels;

namespace MyWebSite.Custom
{
    public class SiteService : ISiteService
    {
        private readonly IUmbracoContextFactory _umbracoContextFactory;

        public SiteService(IUmbracoContextFactory umbracoContextFactory)
        {
            _umbracoContextFactory = umbracoContextFactory;

        }
        public Website GetWebsite(int id)
        {
            Website website = null;
           
            using (UmbracoContextReference umbracoContextReference = _umbracoContextFactory.EnsureUmbracoContext())
            {

                website = umbracoContextReference.UmbracoContext.Content.GetById(id).AncestorOrSelf(Website.ModelTypeAlias) as Website;
            }

            return website;
        }

        public SearchPage GetSearchPage(int id)
        {
            SearchPage searchpage = null;
           
           

            using (UmbracoContextReference umbracoContextReference = _umbracoContextFactory.EnsureUmbracoContext())
            {

                searchpage = GetWebsite(id).ChildrenOfType(SearchPage.ModelTypeAlias) as SearchPage;
            }

            return alias;
        }
    }
}

UmbracoHelperExtensions.cs

using LightInject;
using Umbraco.Core;
using Umbraco.Web;
using Umbraco.Web.PublishedModels;

namespace  MyWebSite.Custom
{
    public static class UmbracoHelperExtensions
    {
        public static Website GetWebsite(this UmbracoHelper umbracoHelper)
        {

            var siteService = Umbraco.Web.Composing.Current.Factory.GetInstance<ISiteService>();

            return siteService.GetWebsite(umbracoHelper.AssignedContentItem.Id);
        }

        public static SearchPage GetSearchPage(this UmbracoHelper umbracoHelper)
        {

            var siteService = Umbraco.Web.Composing.Current.Factory.GetInstance<ISiteService>();

            return siteService.GetSearchPage(umbracoHelper.AssignedContentItem.Id);
        }
    }
}

viewsnippet.cshtml

 @if (Umbraco.GetWebsite().MainNavigation.Any())
{
    <ul class="navbar-nav ml-auto">
        @foreach (var link in Umbraco.GetWebsite().MainNavigation)
        {
            <li class="nav-item">
                <a class="nav-link" href="@link.Url" target="@link.Target">@link.Name</a>
            </li>
        }
    </ul>
}


 @if (Umbraco.GetSearchPage() != null)
{
    <form method="post" action="@Umbraco.GetSearchPage().Url">
        <input name="q" type="text" />
         <input type="submit" value="Submit">
    </form>
}