Here is the code. The field I am indexing and searching is Contents.

using System.Data;
using System.Data.SqlClient;
using System.Data.SqlTypes;
using System.Collections;
using Microsoft.SqlServer.Server;
using Lucene.Net;
using Lucene.Net.Search;
using Lucene.Net.Documents;
using Lucene.Net.QueryParsers;
using Lucene.Net.Analysis;
using Lucene.Net.Analysis.Standard;

public partial class UserDefinedFunctions
{

   [Microsoft.SqlServer.Server.SqlFunction(DataAccess =
DataAccessKind.Read,
   FillRowMethodName = "FillRow", SystemDataAccess =
SystemDataAccessKind.Read, TableDefinition = "PK int")]
   public static IEnumerable LuceneSearch(string SearchPhrase)
   {
       Searchable[] remoteSearch = new Searchable[7];
       remoteSearch[0] = new IndexSearcher("//10.0.0.1/14");
       remoteSearch[1] = new IndexSearcher("//10.0.0.2/15");
       remoteSearch[2] = new IndexSearcher("//10.0.0.3/16");
       remoteSearch[3] = new IndexSearcher("//10.0.0.4/17");
       remoteSearch[4] = new IndexSearcher("//10.0.0.4/18");
       remoteSearch[5] = new IndexSearcher("//10.0.0.4/18a");
       remoteSearch[6] = new IndexSearcher("//10.0.0.4/19");
       ParallelMultiSearcher searcher = new
ParallelMultiSearcher(remoteSearch);

       QueryParser qp = new QueryParser("Contents", new
Lucene.Net.Analysis.Standard.StandardAnalyzer());
       Query query = qp.Parse(SearchPhrase);

       Hits hits = searcher.Search(query);

       int[] PKs = new int[hits.Length()];
       for (int i = 0; i < hits.Length(); i++)
       {
         Document doc = hits.Doc(i);
         PKs[i] = int.Parse(doc.Get("PK"));
       }

       return postids ;
   }

   public static void FillRow(object row, out int PK)
   {
       PK= (int)row ;
   }

};