Got this working now using the following.
Had to use an array of the MNTP aliases to compare to, not ideal, but is all good.

private readonly string[] MntpFields = new[] { "offices", "location", "sectors", "services", "people" };

private void IndexMNTP(IndexingNodeDataEventArgs e)
{
    if (e.IndexType != IndexTypes.Content) return;

    var fields = new Dictionary<string, string>(e.Fields);

    foreach (KeyValuePair<string, string> field in fields)
    {
        string key = field.Key;
        string value = field.Value;
        if (MntpFields.Contains(key))
        {
            value = value.Replace(",", " ");
            e.Fields.Add("_" + key, value);
        }
    }

}

Hi Rory

I thought I'll add this, this is a part of my startup events class, just add this and it will make examine searching on __path and custom csv fields possible

Search on __luceneFriendlyAncestors to get ancestors or search for __luceneFriendlyArticleSection if you have a property called articleSection

I have also included one for the InternalMemberIndexSet.

You will need to create your own Index set which is using the Lucene.Net.Analysis.Standard.StandardAnalyzer

Please excuse the non relevant using statements

Thanks Peter Rizk

http://www.wiliam.com.au/wiliam-blog/searching-for-all-descendants-of-a-node-with-umbraco-6-and-examine 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Web.Profile;
using umbraco.BusinessLogic;
using umbraco.cms.businesslogic.member;
using Umbraco.Core;
using Umbraco.Core.Logging;
using Umbraco.Core.Services;
using Umbraco.Core.Models;
using Umbraco.Core.Persistence;
using System.IO;
using System.Drawing;
using System.Web.Hosting;
using umbraco;
using System.Collections;
using System.Web.Routing;
using System.Web.Http;
using Examine.LuceneEngine;
using Examine.LuceneEngine.Providers;
using Examine;
public class RegisterStartupEvents : ApplicationEventHandler
{
    protected override void ApplicationStarted(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
    {
        // add ancestor indexing
        foreach (LuceneIndexer indexer in ExamineManager.Instance.IndexProviderCollection)
        {
            if (indexer.IndexSetName == "CustomIndexSet")
            {
                indexer.DocumentWriting += indexer_DocumentWriting;
            }
            if (indexer.IndexSetName == "InternalMemberIndexSet")
            {
                indexer.DocumentWriting += indexer_DocumentWritingMember;
            }
        }
    }
    protected void indexer_DocumentWriting(object sender, DocumentWritingEventArgs e)
    {
        var luceneDocument = e.Document;
        var p = e.Fields["__Path"];
        if (!String.IsNullOrEmpty(p))
        {
            var newVal = p.Replace(",", " ");
            luceneDocument.Add(new Lucene.Net.Documents.Field("__luceneFriendlyAncestors", newVal, Lucene.Net.Documents.Field.Store.YES, Lucene.Net.Documents.Field.Index.ANALYZED));
        }
        try
        {
            var q = e.Fields["articleSection"];
            if (!String.IsNullOrEmpty(q))
            {
                var newVal = q.Replace(",", " ");
                luceneDocument.Add(new Lucene.Net.Documents.Field("__luceneFriendlyArticleSection", newVal, Lucene.Net.Documents.Field.Store.YES, Lucene.Net.Documents.Field.Index.ANALYZED));
            }
        }
        catch (Exception ex)
        {
            // LogHelper.Error(GetType(), string.Format("Error adding index field for {0}", e.Fields["nodeName"]), ex);
        }
    }

    protected void indexer_DocumentWritingMember(object sender, DocumentWritingEventArgs e)
    {
        try
        {
            var luceneDocument = e.Document;
            var p = e.Fields["_contributorType"];
            if (p != null)
            {
                var newVal = p.Replace(",", " ");
                luceneDocument.Add(new Lucene.Net.Documents.Field("__luceneFriendlyContributorType", newVal, Lucene.Net.Documents.Field.Store.YES, Lucene.Net.Documents.Field.Index.ANALYZED));
            }
        }
        catch (Exception ex)
        {
            // LogHelper.Error(GetType(), string.Format("Error adding index field for {0}", e.Fields["nodeName"]), ex);
        }
    }
}

Rory (?),

I am having the same issue but do not know how to look up the node names from within my custom indexer class that derives from BaseUmbracoIndexer. I do not have access to ServiceContext.ContentService.GetById() to look them up.

Thoughts?

Regards, Alan

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