C# to HTML Converter with syntax highlighting

C# to HTML Converter with syntax highlighting/colouring ver. 1.0.44.

Paste some C# code (it doesn't have to be working/valid code) and give it a try!

Or try it on some GitHub's repo: https://csharp-colors.xyz/GitHub

Source Code: https://github.com/Swiftly1/CsharpToColouredHTML

Add Line Numbers
Enable Optimizations - decreases generated HTML size, but generated CSS may be different for different code fragments, so if you're using custom CSS then you need to pay attention. More info in Customizability docs
Use Iframe - generates iframe with inlined, escaped HTML of the code. This is not necessary, but makes embedding on your website easier, since it isolates generated HTML/CSS from your, so they don't break eachother. If you want pure, unescaped HTML then disable this.
Lines Highlighting:

using System;
using System.Collections.Generic;
using System.Runtime.CompilerServices;

namespace DictionaryList
{
    public class DictionaryList<T, U>
    {
        private readonly Node<T, U> Root = new Node<T, U>(default!, null) { IsRoot = true };

        /// <summary>
        /// This parameter indicates whether key contains NULLs e.g [UserA, null, new User()].
        /// Allowing NULLs within keys has some performance - speed and memory penalty, that's why it is disabled by default.
        /// </summary>
        public bool AllowNULLsInKeys { get; set; }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="allow_keys_with_nulls">This parameter indicates whether key contains NULLs e.g [UserA, null, new User()].
        /// Allowing NULLs within keys has some performance - speed and memory penalty, that's why it is disabled by default.</param>
        public DictionaryList(bool allow_keys_with_nulls = false)
        {
            AllowNULLsInKeys = allow_keys_with_nulls;
        }

        public void Add(List<T> data, U value)
        {
            var current = Root;

            for (int i = 0; i < data.Count; i++)
            {
                T item = data[i];

                if (!AllowNULLsInKeys && item == null)
                    throw new ArgumentException($"Element at index '{i}' is NULL. It cannot be used as a Key's element. " +
                        $"If you want to use NULLs inside Keys, then either use constructor 'DictionaryList(true)' or set property 'AllowNULLsInKeys' to true.");

                Node<T, U> found = FindNode(current, item);

                var isLast = i == data.Count - 1;

                if (found != null)
                {
                    if (isLast)
                    {
                        if (found.StoredValue is null)
                        {
                            found.StoredValue = new ValueWrapper<U>(true, value);
                        }
                        else
                        {
                            if (found.StoredValue.HasValue && !found.StoredValue.Value!.Equals(value))
                            {
                                throw new ArgumentException($"Value: '{value}' cannot be saved because there's already value:" +
                                    $" {found.StoredValue.Value}. Key: {string.Join(",", data)}");
                            }
                        }
                    }

                    current = found;
                }
                else
                {
                    var wrapper2 = new ValueWrapper<U>(isLast, value);
                    current = current.Add(item, wrapper2);
                }
            }
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private Node<T, U> FindNode(Node<T, U> current, T item)
        {
            if (AllowNULLsInKeys)
            {
                for (int i = 0; i < current.Children.Count; i++)
                {
                    if (Equals(current.Children[i].ArrayValue, item))
                        return current.Children[i];
                }
            }
            else
            {
                for (int i = 0; i < current.Children.Count; i++)
                {
                    if (current.Children[i].ArrayValue!.Equals(item))
                        return current.Children[i];
                }
            }

            return null;
        }

        public bool TryGet(List<T> data, out U? value)
        {
            var current = Root;

            for (int i = 0; i < data.Count; i++)
            {
                T item = data[i];

                Node<T, U> found = FindNode(current, item);

                var isLast = i == data.Count - 1;

                if (found != null)
                {
                    if (isLast)
                    {
                        if (found.StoredValue == null || !found.StoredValue.HasValue)
                            goto Fail;

                        value = found.StoredValue.Value;
                        return true;
                    }

                    current = found;
                }
                else
                {
                    goto Fail;
                }
            }

            Fail:
            value = default;
            return false;
        }
    }
}