title: ignore case sensitive in regex.replace?
body: <p>I have this code to search in a string and replace some text with other text:</p>
  
  <pre><code>Regex regexText = new Regex(textToReplace);
  retval = regexText.Replace(retval, Newtext);
  </code></pre>
  
  <p><code>textToReplace</code> may be "welcome" or "client" or anything.</p>
  
  <p>I want to ignore case for <code>textToReplace</code> so that "welcome" and "Welcome" both match.</p>
  
  <p>How can I do this?</p>