How to stop rewriting of index Lucene.net c#?

Question

I was been doing indexing using lucene.net in WPF C# and suddenly got that new every new doc was added instead of previous and thus the any moment number of docs in index was 1

I don't know how can this happen because I have tested the same adding methods in C# Console but in forms it just something strange happen

Can't you suggest how to solve the problem?

This is the code of where the method to create index is called

private void btnAdd_Click(object sender, RoutedEventArgs e)
    {
        try
        {
            LuceneSearch.LuceneEngine le = new LuceneSearch.LuceneEngine();
           var engine = new FileEngine();

            if (txtboxName.Text != "" && cmbboxDis.SelectedIndex != -1 && btnFile.Content.ToString() != "Choose a file")
            {//adds some stuff to DB and returns an object to index
               var IndexMe= engine.AddFile(txtboxName.Text, cmbboxDis.SelectedIndex, txtboxAuth.Text, txtboxTags.Text, txtboxComment.Text);
                le.BuildIndex(IndexMe);//index this file

                this.Close();
            }
            else
                MessageBox.Show("Not all fields are filled", "Oops!", MessageBoxButton.OK, MessageBoxImage.Error);
        }
        catch (Exception ex)
        {
            MessageBox.Show("You haven't chosen a file! " +ex.Message, "Ошибка!", MessageBoxButton.OK, MessageBoxImage.Error);
        }
    }

That's the way how it looks in class of lucene methods

namespace StudentWorksSearch.LuceneSearch
{
public  class LuceneEngine
{//get directory
      private const string _luceneDir = "../../../Data/lucene_index1";
    private   FSDirectory _directoryTemp;
    private    FSDirectory _directory
    {
        get
        {
            if (_directoryTemp == null) _directoryTemp = FSDirectory.Open(new
        DirectoryInfo(_luceneDir));
            if (IndexWriter.IsLocked(_directoryTemp)) IndexWriter.Unlock(_directoryTemp);
            var lockFilePath = Path.Combine(_luceneDir, "write.lock");
            if (File.Exists(lockFilePath)) File.Delete(lockFilePath);
            return _directoryTemp;
        }
    }


    //this method creates document from an ObjectToIndex
    public   void BuildIndex(FileToIndex file)
    {
        using (var analyzer = new Lucene.Net.Analysis.Ru.RussianAnalyzer(Version.LUCENE_30))
        {
            using (IndexWriter idxw = new IndexWriter(_directory, analyzer, true, IndexWriter.MaxFieldLength.UNLIMITED))
            {
                //check if document exists, if true deletes existing                    
                var searchQuery = new TermQuery(new Term("Id", file.Id.ToString()));
                idxw.DeleteDocuments(searchQuery);
                //creation
                Document doc = new Document();
                doc.Add(new Field("Id", file.Id.ToString(), Field.Store.YES, Field.Index.NOT_ANALYZED));//аналайзер разбивает строки на слова
                doc.Add(new Field("Title", file.Title, Field.Store.YES, Field.Index.ANALYZED));
                doc.Add(new Field("Description", file.Description, Field.Store.YES, Field.Index.ANALYZED));
                doc.Add(new Field("Authors", file.Authors, Field.Store.YES, Field.Index.ANALYZED));
                doc.Add(new Field("Text", file.Text, Field.Store.YES, Field.Index.ANALYZED));
                doc.Add(new Field("Hashtags", file.Hashtags, Field.Store.YES, Field.Index.ANALYZED));
                //write the document to the index
                idxw.AddDocument(doc);

                //optimize and close the writer
                idxw.Commit();

                idxw.Optimize();                  
            }
        }
    }

Answer 1

The third argument to the IndexWriter constructor specifies whether it should create a new index. If it is set to true, it will overwrite any existing index and create a new one. You should set it to false to open an existing index:

IndexWriter idxw = new IndexWriter(_directory, analyzer, false, IndexWriter.MaxFieldLength.UNLIMITED