I am trying to use RegEx to replace a string, but nothing is being replaced. I'm not sure what I'm doing wrong.

```
System.Text.RegularExpressions.Regex regEx = null;

regEx = new System.Text.RegularExpressions.Regex("DefaultStyle.css?x=839ua9");
pageContent = regEx.Replace(htmlPageContent, "DefaultStyleSnap.css?x=742zh2");

```

**htmlPageContent** is of type string, and contains the html page content of the Render method (write before we send it to the browser). The htmlPageContent string definitely contains "DefaultStyle.css?x=839ua9". I can see it when I do Quick Watch in visual studio, and when I view Page Source. 

Why is RegEx not replacing the string?