Regex.Replace HowTo
<p>I'm trying to find the patteren which replace the string includes <code>"System"</code> followed by dots underscore and digit... for expmple 
to replace </p>

<pre><code>"class [System.Windows.Forms_20]System.Windows.Forms.MouseEventHandler"
</code></pre>

<p>with </p>

<pre><code>class [System.Windows.Forms_]System.Windows.Forms.MouseEventHandler
</code></pre>
