代码使用

<ddc:CustomDropDown ID="Countries" 
InnerText="<%$ Resources:Resource, CountriesCombo%>" runat="server" 
Width="320px" style="margin-top:5px" Separator="@"></ddc:CustomDropDown>

关键原理 

protected override void InitializeCulture()
    {
        string lang = "en-US";
        if (Request.QueryString["lang"] != null)
        {
            switch (Request.QueryString["lang"])
            {
                case "rus":
                    lang = "ru-RU";
                    break;
                case "eng":
                    lang = "en-US";
                    break;
            }
        }
        System.Globalization.CultureInfo ci = new
                     System.Globalization.CultureInfo(lang);
        System.Threading.Thread.CurrentThread.CurrentCulture = ci;
        System.Threading.Thread.CurrentThread.CurrentUICulture = ci;
        base.InitializeCulture();
    }