The Controls collection cannot be modified because the control contains code blocks (i.e. <% ... %>)
<p>I am trying to add a css   form code .  My website uses a master page .  I am getting the error The Controls collection cannot be modified because the control contains code blocks (i.e. &lt;% ... %>). </p>

<p>my code snipet </p>

<pre><code>string CssClass = string.Format("{0}/{1}?$BUILD$", BaseImageUrl, CssFileName);

HtmlLink css = new HtmlLink();
            css.Href = CssClass;
            css.Attributes["rel"] = "stylesheet";
            css.Attributes["type"] = "text/css";
            Header.Controls.Add(css);
</code></pre>

<p>Any suggestions?</p>
