public class MiaPagina : System.Web.UI.Page
    {
            ProfileCommon CurrentProfile = (ProfileCommon)HttpContext.Current.Profile;

            if (!Thread.CurrentThread.CurrentCulture.Name.Equals(CurrentProfile.Lingua))
            {
                Thread.CurrentThread.CurrentCulture = CultureInfo.CreateSpecificCulture(CurrentProfile.Lingua);
                Thread.CurrentThread.CurrentUICulture = new CultureInfo(CurrentProfile.Lingua);
            }
    }

public partial class SwitchLanguage : System.Web.UI.UserControl
{
    protected void ChangeLanguage(object sender, ImageClickEventArgs e)
    {        
        ImageButton Flag = (ImageButton) sender;

        Profile.Lingua = Flag.CommandArgument;
        Profile.Save();
    }
}

Thread.CurrentThread.CurrentCulture

Profile.Lingua