Speech to text dictation in an ASP.NET Core rich text editor

Some people think faster than they type, and others cannot type easily at all. Dictation adds a microphone button that turns speech into text in the editor.

Turn it on

<richtextbox asp-for="Body"
             toolbar="default"
             enable-dictation="true"
             dictation-lang="en-US"
             dictation-continuous="true"
             dictation-auto-punctuation="true"></richtextbox>

Press the microphone, then speak. Words appear under the caret as they are recognized, and the button shows that it is listening. Press it again to stop.

Which language

dictation-lang takes a language tag, such as de-DE or zh-CN. Set it from the user's language:

dictation-lang="@System.Globalization.CultureInfo.CurrentUICulture.Name"

From code

var editor = window.richTextBoxEditors.Body;

if (editor.dictation.isSupported()) {
    editor.dictation.start();
}
editor.dictation.stop();
editor.dictation.toggle();
editor.dictation.isListening();

What to know

It relies on the browser. It uses the Web Speech API, so support varies. Check isSupported() and do not rely on it as the only way to write.
Your server is not involved. You need no service and no key. In some browsers, though, the browser's vendor processes the audio, so check this against your privacy rules.
HTTPS is needed. Browsers only give microphone access on a secure page, other than on localhost.