Pastable version of Balance HTML Tags

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            <pre class="sunburst"><span style="color:#E28964;">private</span> <span style="color:#E28964;">static</span> Regex _namedtags = <span style="color:#E28964;">new</span> Regex
    (@<span style="color:#65B042;"><span style="color:#65B042;">&quot;</span>&lt;/?(?&lt;tagname&gt;<span style="color:#DDF2A4;">\w</span>+)[^&gt;]*(<span style="color:#DDF2A4;">\s</span>|$|&gt;)<span style="color:#65B042;">&quot;</span></span>,
    RegexOptions.Singleline | RegexOptions.ExplicitCapture);

<span style="color:#AEAEAE;font-style:italic;"><span style="color:#AEAEAE;font-style:italic;">//</span>/ &lt;summary&gt;</span>
<span style="color:#AEAEAE;font-style:italic;"><span style="color:#AEAEAE;font-style:italic;">//</span>/ attempt to balance HTML tags in the html string</span>
<span style="color:#AEAEAE;font-style:italic;"><span style="color:#AEAEAE;font-style:italic;">//</span>/ by removing any unmatched opening or closing tags</span>
<span style="color:#AEAEAE;font-style:italic;"><span style="color:#AEAEAE;font-style:italic;">//</span>/ &lt;/summary&gt;</span>
<span style="color:#E28964;">public</span> <span style="color:#E28964;">static</span> <span style="color:#99CF50;">string</span> BalanceTags(<span style="color:#99CF50;">string</span> html)
{
    var tagname = <span style="color:#65B042;"><span style="color:#65B042;">&quot;</span><span style="color:#65B042;">&quot;</span></span>;
    var tag = <span style="color:#65B042;"><span style="color:#65B042;">&quot;</span><span style="color:#65B042;">&quot;</span></span>;
    var ignoredtags = <span style="color:#65B042;"><span style="color:#65B042;">&quot;</span>&lt;p&lt;img&lt;br&lt;li<span style="color:#65B042;">&quot;</span></span>;
    var match = <span style="color:#3387CC;">0</span>;

MatchCollection tags = _namedtags.Matches(html);
    <span style="color:#99CF50;">bool</span>[] tagpaired = <span style="color:#E28964;">new</span> <span style="color:#99CF50;">bool</span>[tags.Count];

<span style="color:#AEAEAE;font-style:italic;"><span style="color:#AEAEAE;font-style:italic;">//</span> loop through matched tags in reverse order</span>
    <span style="color:#E28964;">for</span> (<span style="color:#99CF50;">int</span> i = tags.Count - <span style="color:#3387CC;">1</span>; i &gt; -<span style="color:#3387CC;">1</span>; i--)
    {
        tagname = tags[i].Groups[<span style="color:#65B042;"><span style="color:#65B042;">&quot;</span>tagname<span style="color:#65B042;">&quot;</span></span>].Value.ToLower();
        tag = tags[i].Value;
        match = -<span style="color:#3387CC;">1</span>;

<span style="color:#AEAEAE;font-style:italic;"><span style="color:#AEAEAE;font-style:italic;">//</span> skip any tags in our ignore list; assume they're self-closed</span>
        <span style="color:#E28964;">if</span> (!tagpaired[i] &amp;&amp; !ignoredtags.Contains(<span style="color:#65B042;"><span style="color:#65B042;">&quot;</span>&lt;<span style="color:#65B042;">&quot;</span></span> + tagname))
        {
            <span style="color:#E28964;">if</span> (tag.StartsWith(<span style="color:#65B042;"><span style="color:#65B042;">&quot;</span>&lt;/<span style="color:#65B042;">&quot;</span></span>))
            {
                <span style="color:#AEAEAE;font-style:italic;"><span style="color:#AEAEAE;font-style:italic;">//</span> if searching backwards, look for opening tags</span>
                <span style="color:#E28964;">for</span> (<span style="color:#99CF50;">int</span> j = i - <span style="color:#3387CC;">1</span>; j &gt; -<span style="color:#3387CC;">1</span>; j--)
                {
                    <span style="color:#E28964;">if</span> (!tagpaired[j] &amp;&amp; tags[j].Value.ToLower().StartsWith(<span style="color:#65B042;"><span style="color:#65B042;">&quot;</span>&lt;<span style="color:#65B042;">&quot;</span></span> + tagname))
                    {
                        match = j;
                        <span style="color:#E28964;">break</span>;
                    }
                }
            }
            <span style="color:#E28964;">else</span>
            {
                <span style="color:#AEAEAE;font-style:italic;"><span style="color:#AEAEAE;font-style:italic;">//</span> if searching forwards, look for closing tags</span>
                <span style="color:#E28964;">for</span> (<span style="color:#99CF50;">int</span> j = i + <span style="color:#3387CC;">1</span>; j &lt; tags.Count; j++)
                {
                    <span style="color:#E28964;">if</span> (!tagpaired[j] &amp;&amp; tags[j].Value.ToLower().StartsWith(<span style="color:#65B042;"><span style="color:#65B042;">&quot;</span>&lt;/<span style="color:#65B042;">&quot;</span></span> + tagname))
                    {
                        match = j;
                        <span style="color:#E28964;">break</span>;
                    }
                }
            }

<span style="color:#E28964;">if</span> (match &gt; -<span style="color:#3387CC;">1</span>)
            {
                <span style="color:#AEAEAE;font-style:italic;"><span style="color:#AEAEAE;font-style:italic;">//</span> found matching opening/closing tag</span>
                tagpaired[match] = <span style="color:#E28964;">true</span>;
                tagpaired[i] = <span style="color:#E28964;">true</span>;
            }
            <span style="color:#E28964;">else</span>
            {
                <span style="color:#AEAEAE;font-style:italic;"><span style="color:#AEAEAE;font-style:italic;">//</span> no matching opening/closing tag found -- remove this tag!</span>
                html = html.Remove(tags[i].Index, tags[i].Length);
                tagpaired[i] = <span style="color:#E28964;">true</span>;
                System.Diagnostics.Debug.WriteLine(<span style="color:#65B042;"><span style="color:#65B042;">&quot;</span>unbalanced tag removed: <span style="color:#65B042;">&quot;</span></span> + tags[i]);
            }
        }
    }

<span style="color:#E28964;">return</span> html;
}
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