Geshi code highlighter does not work

Question

I am using Geshi code highlighter in Joomla 3.8.1 but it does not work.

I have enabled both "Content - Script Code Highlighter (GeSHi)" and "Button - Script Code Highlighter (GeSHi)", and in fact, button appears when I edit the article.

When I add in content, for example,

<pre xml:lang="csharp">[code]
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Text;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Drawing;
namespace Desytec.Web.UI.WebControls
{
    [ToolboxBitmap(typeof(RutValidator), "RutValidator.bmp")]
    [ToolboxData("&lt;{0}:RutValidator runat=\"server\"&gt;&lt;/{0}:RutValidator&gt;")]
    public class RutValidator : BaseValidator
    {
    }
}[/code]</pre>

This is the result in frontend:

What may be happening here?

Answer 1

Did you follow the steps mentioned here https://scriptplaza.com/component/content/article/97-latest-news/12-test.html?Itemid=101.

before that go to Tiny MCE plugin and enable extended functionality.

Also did you asked in their forum.