Hi Brad

I know its late to reply but I've just been trying to do something similar this afternoon. I wanted to check to see if the client resource manager had already add a CSS file or not. 

As you say DNN fail to explain how to reference the Page object which you would get in a Webform page. Without this reference to the object the razor scripts are limited. 

The solution is pretty simply once you start digging into the sourcecode and use ILSpy. This is the code I've wrote to get access to the page, then look in the header for the CSS that would have been registered by other modules. If the header with the correct CSS file doesn't exist we just add it from the razor code block. 

The object to use is Context.CurrentHandler then cast is back to the Page. From there its pretty simple code to do the check.

@using DotNetNuke.Web.Client.ClientResourceManagement;

@{
var p2 = Context.CurrentHandler as Page;

bool foundTarget = false;
string cssName = "/Portals/0/CVStore/ResponsiveTemplates/StyleSheet/font-awesome.min.css";

foreach(var c in p2.Header.Controls){

var headerCss = c as DnnCssInclude;
if(headerCss != null){
if(headerCss.FilePath == cssName.ToLower()){
foundTarget = true;
}
}
}

if(!foundTarget){
ClientResourceManager.RegisterStyleSheet(p2, cssName);
}
}