How to add style from code behind?

I want to add a style A:Hover to a HyperLink control from code behind.

I can do like this :

HyperLink hlRow = new HyperLink();
hlRow.Style.Add("color", "#000000");
hlRow.Style.Add("text-decoration", "none");

But how can I add styles for A:Hover for the hyperlink control? Do I need to define a class and associate that class with this control, if yes how?