How do you programmatically apply a css class to an asp.net control?

Question

I\'m wondering how I can apply a CSS class to an ASP.NET Control (TextBox in this case) through the backend in C#. For example:

Answer 1

Simply create an entry in the ViewDataDictionary for the class.

The backend would look something like

ViewData["selectedclass"] = <conditionalstatement> ? "selected" : "";

And the view would be

    <asp:TextBox ID="firstName" CssClass="input left <%= ViewData["selectedclass"]%>" runat="server" Text="First Name" />