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

I find it better to use REGEX replace since replacing class could exist as partial name in other classes which would break them. So I'm using the following extension method:

public static void RemoveClass(this WebControl control, string classToRemove)
{
    if (control == null)
        return;

    control.CssClass = Regex.Replace(control.CssClass, @"(^|\s)" + classToRemove + @"($|\s)", " ");
}