New Post: Add class to body

Short answer, depends.

Long answer; its definitely easiest if your Template is based on Masterpage (WebForms) due to its Lifecycle pipeline.

For instance, you can in your function do

HttpContext.Current.Items["bodyClass"] = "someBodyClass".

In your Template you mark your body-tag with a runat="server" attribute, and in your PreRender event you add pull out the value from

HttpContext.Current.Items["bodyClass"]

and assign it to the body.