Load custom dictionary just once. Wpf spellchecker

Question

So, here is the code:

IList dictionaries = SpellCheck.GetCustomDictionaries(tb);
Uri uri = new Uri("Russian.lex", UriKind.Relative);
dictionaries.Add(uri);
tb.SpellCheck.IsEnabled = true;

The thing is, that I have to create multiple textboxes with spellcheck, and the only way to assign a customdictionary is to pass the Uri to the TextBoxBase.CustomDictionaries.Add(). So every time I set SpellCheck.IsEnabled there is a 3-5 sec lag, which in my opinion is caused by loading file from the harddisk. On top of that it seems that every time the dictionary is loaded it stays in memory for eternity.

Any tips on how can I load custom dictionary once and than re-use it?

John Melville · Accepted Answer

After many false starts, I think I have made it work.

I scrounged around with reflection until I found the internal representation (ILexicon) for the custom dictionary. I then assigned this ILexicon to each new text content. None of these interfaces are public, and so I run the obvious risk of being broken in future versions, or even a service pack, but it works for today. [This breaks and becomes unnecessary in .net 4.6 see below.]

using System;
using System.Collections;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Runtime.InteropServices;
using System.Security;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using Melville.Library.ReflectionHelpers;

namespace PhotoDoc.Wpf.Controls.FormControls
{
  public static class DynamicDictionaryLoader
  {
    private static string dictionaryLocation;
    public static string DictionaryLocation
    {
      get
      {
        if (dictionaryLocation == null)
        {
          var path = Path.GetDirectoryName(Assembly.GetExecutingAssembly().GetName().CodeBase);
          dictionaryLocation = Path.Combine(path, "UsMedicalEnglish.dic");
        }
        return dictionaryLocation;
      }
    }

    public static void AddDictionary(TextBoxBase targetControl)
    {
      try
      {
        InnerLoadDictionary(targetControl);
      }
      catch (UriFormatException)
      {
        // occasionaly occurrs in odd instalations.  You just don't get the medical dictionary
      }
      catch (ArgumentException)
      {
        // this is a rare bug that I think may be a race condition inside WPF.  I've only triggered it 2-3 times.
        // One time was when I had seven files open at once.  The other, ironically, was when activating the
        // default text for a field.  

        // In this rare error exception, you will just get all your medical words flagged as mispellings for that
        // textbox.  I won't know for a while if this worked, because I only saw the bug after months of daily use
        // of the program.
      }
    }

    private static object oldDictionary = null;
    private static object dictionaryLoaderLock = new Object();

    private static void InnerLoadDictionary(TextBoxBase targetControl)
    {
      var dictionary = SpellCheck.GetCustomDictionaries(targetControl);
      if (dictionary.Count < 1)
      {
          var speller = dictionary.GetProperty("Speller");
          var uriMap = speller.GetProperty("UriMap") as IDictionary;
          if (uriMap.Count > 0) return; // already initalized
          lock (dictionaryLoaderLock)
          {
            var dictionaryUri = new Uri(DictionaryLocation, UriKind.Absolute);
            if (oldDictionary == null)
            {
              dictionary.Add(dictionaryUri);
              oldDictionary = uriMap.Values.OfType

Load custom dictionary just once. Wpf spellchecker

Answers (2)

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