WPF Custom Dictionary is NOT working after Windows Server 2019 and Windows 10 latest versions

Question

We are running a old WPF application and due to some reasons stick with .NET 4.5 version only.

Using the following code, we are adding some custom dictionaries for every RichTextbox controls.

public void InitDictionary()
{
    var dictionaries = SpellCheck.GetCustomDictionaries(richText);
    if (dictionaries.Count == 0)
    {
        var dictionaryUri = TextBoxDictionary.DictionaryUri;
        if (dictionaryUri != null)
        {
            dictionaries.Add(dictionaryUri);
        }
    }
}

This code is working fine in Windows Server 2016 and Windows 10 1670 version.

But same code is NOT working in Windows Server 2019 and latest versions of Windows 10.

For now, we could not update our application to .Net 4.6.1 or latest version

Since it is working fine in older version of Windows, suspect it is known issue with latest Windows OS. Please correct me if I'm wrong.

Is there any solid fix available without going for third party controls?

Thanks in advance.

Answer 1

Finally we identified that, there is some size limitation on user custom dictionary in Windows!

We are using bigger custom dictionary files (nearly 2mb). And by the following (MS recommended) registry fix is resolving our issue.

HKEY_CURRENT_USER\Software\Microsoft\Spelling\Dictionaries\AllowBiggerUD=1

AllowBiggerUD as DWORD 32-bit

https://learn.microsoft.com/en-us/windows/win32/api/spellcheck/nn-spellcheck-iuserdictionariesregistrar#remarks