Strip Html Markup Tags

StripMarkupTags.cs

private static string StripMarkupTags(string source)
{
    if (source == null) return string.Empty;

    var length = source.Length;
    var array = new ArrayBuilder(length);
    var markup = false;

    for (var i = 0; i < length; i++)
    {
        switch (source[i])
        {
            case '<':
                markup = true;
                continue;
            case '>':
                markup = false;
                continue;
        }

        if (markup) continue;

        array.Add(source[i]);
    }
    return array.ToString();
}

internal struct ArrayBuilder
{
    private readonly char[] _array;

    private int _index;

    internal ArrayBuilder(int capacity)
    {
        _array = new char[capacity];
        _index = 0;
    }

    internal void Add(char item) => _array[_index++] = item;

    public override string ToString() => new string(_array, 0, _index);
}