SpeechSynthesizer.AddLexicon is not respecting the custom overrides

Question

I am using speech synthesizer for converting text to speech. I wanted to use a custom lexicon file so I used the AddLexicon method as recommended on msdn

Here is my function

     public void ReadOut(string sentence)
    {
        using (SpeechSynthesizer synth = new SpeechSynthesizer())
        {
            synth.SelectVoiceByHints(gender: VoiceGender.Male, age: VoiceAge.Adult, voiceAlternate: 1, culture: CultureInfo.CreateSpecificCulture("en-US"));
            synth.Rate = -2;
            var fqn = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
            var uri = new Uri("file://" + fqn + "/CustomLexicon.pls");
            synth.AddLexicon(uri, "application/pls+xml");
            synth.Speak(sentence);
        }

    }

and my lexicon file is

 <?xml version="1.0" encoding="UTF-8"?>
 <lexicon version="1.0" 
  xmlns="http://www.w3.org/2005/01/pronunciation-lexicon"
  alphabet="x-microsoft-ups" xml:lang="en-US">
 <lexeme>
     <grapheme> BLUE </grapheme>
     <phoneme> B L I P </phoneme>
   </lexeme>
</lexicon>

However, when i pass "BLUE" to the function it still outputs BLUE instead of BLIP. Am I missing something?

Note : I made sure that the pls file exists in the right location and its contents are correctly populated.

Answer 1

This appears to be a bug in the System.Speech implementation of the synthesizer, as per the accepted answer here: How do I use a lexicon with SpeechSynthesizer?