Examine search in Umbraco 8

I use a custom index, here called NordmanniIndex, which i then add all the fields available to it, so i can search them. 

public class ExamineComponent : IComponent
    {
        private readonly IExamineManager _examineManager;
        private readonly ILogger _logger;
        private readonly CustomIndexCreator customIndexCreator;

        public ExamineComponent(IExamineManager examineManager, ILogger logger, CustomIndexCreator customIndexCreator)
        {
            _examineManager = examineManager ?? throw new
            ArgumentNullException(nameof(examineManager));
            _logger = logger;
            this.customIndexCreator = customIndexCreator;
        }

        public void Initialize()
        {
            foreach (var dex in customIndexCreator.Create())
            {
                _examineManager.AddIndex(dex);
            }
            if (_examineManager.TryGetIndex("NordmanniIndex", out IIndex customNordmanniIndex))
            {
                if (customNordmanniIndex is BaseIndexProvider indexProviderNordmanni)
                {
                    indexProviderNordmanni.TransformingIndexValues += IndexProviderTransformingIndexValues;
                }
            }
        }
        private void IndexProviderTransformingIndexValues(object sender, IndexingItemEventArgs e)
        {
            if (e.ValueSet.Category == IndexTypes.Content)
            {
                try
                {
                    var combinedFields = new StringBuilder();
                    foreach (var fieldValues in e.ValueSet.Values)
                    {
                        foreach (var value in fieldValues.Value)
                        {
                            if (value != null)
                            {
                                combinedFields.AppendLine(value.ToString());
                            }
                        }
                    }
                    e.ValueSet.Add("contents", combinedFields.ToString());
                }
                catch (Exception ex)
                {
                    _logger.Error<ExamineComponent>(ex, "Error combining fields for {ValueSetId}", e.ValueSet.Id);
                }
            }
        }
        public void Terminate()
        {
        }
    }

Then i have a SearchHelper with a GetSearchResult method. 

Here i search my fields, and exclude certain pages from the result, since i don’t want them to appear in searches. And if a page has the UmbracoNavihide, that should be excluded as well.

public ISearchResults GetSearchResult(string searchTerm = "")
        {
            searchTerm = searchTerm.MakeSearchQuerySafe();

            IExamineManager examineManager = ExamineManager.Instance;
            if (!examineManager.TryGetIndex("NordmanniIndex", out IIndex index))
            {
                throw new InvalidOperationException($"No index found by name NordmanniIndex");
            }

            var searcher = index.GetSearcher();
            var fieldToSearch = "contents";
            var hideFromNavigation = "umbracoNaviHide";
            var criteria = searcher.CreateQuery(IndexTypes.Content, BooleanOperation.Or);
            var examineQuery = criteria.Field(fieldToSearch, searchTerm);
            new ContentValueSetValidator(true, true, publicAccessService, null, null, null);
            if (searchTerm.Contains(" "))
            {
                var terms = searchTerm.Split(' ').Select(x => x.MultipleCharacterWildcard()).ToArray();
                examineQuery.And().GroupedOr(new[] { fieldToSearch }, terms);
            }
            else
            {
                examineQuery.And().Field(fieldToSearch, searchTerm.MultipleCharacterWildcard());
            }

            // if hidden from navigation, should also not be shown in search.
            examineQuery.Not().Field(hideFromNavigation, 1.ToString());

            //exclude these Document types from searches:
            examineQuery.Not().NodeTypeAlias(NotFound.ModelTypeAlias);
            examineQuery.Not().NodeTypeAlias(Global.ModelTypeAlias);
            examineQuery.Not().NodeTypeAlias(AdminSection.ModelTypeAlias);

            var results = examineQuery.Execute();

            if (results.Any())
            {
                return results;
            }
            else
            {
                return null;
            }
        }