TWebHTMLContainer - Copy rendered content and Paste it somewhere else

I would like to select the content of a TWebHTMLContainer and copy it to the clipboard,
like I can do with any other web page.
Please advise on how to accomplish this.
Thank you!

Add a class like:

    <style>
    .containerselect { user-select: auto; }
    </style>

and set this class to your TWebHTMLContainer.ElementClassName

WebHTMLContainer.ElementClassName := 'containerselect';

my project has several units hence several html files. Which html file should I use for inserting the class?
I tried index.html, however, no effect

The main app HTML file should work.
I tested it here and it works. Verify via the brower console the CSS class is available and properly hooked up.

It didn't work for me the way you described it, however, it works if I add the class to my html text the container is hostingšŸ˜€
.selectall {
-moz-user-select: all;
-webkit-user-select: all;
-ms-user-select: all;
user-select: all;
}