Remove a CSS class from HTML element in the code behind file

Question

I have the following on my interface / webform:

Now I have a condition in my

Answer 1

public static void appendCssClass(HtmlGenericControl htmlGenericControl, string cssClassName)
    {
        htmlGenericControl.Attributes.Add("class", 
            htmlGenericControl.Attributes["class"].ToString() + " " + cssClassName);
    }

    public static void removeCssClass(HtmlGenericControl htmlGenericControl, string cssClassName)
    {
        htmlGenericControl.Attributes.Add("class",
                    htmlGenericControl.Attributes["class"].Replace(cssClassName, ""));
    }