The question has been asked (and answered) already:
Render View as a String
This is the bit that I use:
protected string RenderViewToString<T>(string viewPath, T model, System.Web.Mvc.ControllerContext controllerContext) {
using (var writer = new StringWriter()) {
var view = new WebFormView(viewPath);
var vdd = new ViewDataDictionary<T>(model);
var viewCxt = new ViewContext(controllerContext, view, vdd, new TempDataDictionary(), writer);
viewCxt.View.Render(viewCxt, writer);
return writer.ToString();
}
}
Best place for this method is in a class library project that your mvc project has a reference to. Mainly because that way you can easily reuse it in all your apps. But also because it is neither Application logic (so doesn't belong in the controller) nor does it belong in the model. Some things are just utilities.
Note that to get this to work, the viewPath parameter HAS to be the PHYSICAL PATH to the file, complete with the .aspx extension. You can't use a route as WebFormView class requires a physical path in its constructor.
This will render the full view and take account of the master page.
HEALTH WARNING FOR HTML EMAILS:
HTML emails and the devices where you read them are even more difficult and restrictive to design for than websites and browsers. What works in one, will not work in another. So with html emails, you really have to Keep It Simple! Your lovely page with menus and relative images and whatever else, JUST WON'T WORK in all email devices. Just as an example, the images src attribute needs to be absolute and include the domain:
This won't work:
<img src="/Images/MyImage.gif" ... />
Bit this will:
<img src="http://www.mywebsite.com/Images/MyImage.gif" ... />
With those caveats, it works fine and I use it. Just don't try to send them the full gimmickry of your website, cos that won't work!
Even more important:
All CSS must be INLINE and just for basic styling: colours, borders, padding. But no floating and positioning. CSS layouts won't work consistently across devices!