imports System.Configuration;

public class DataServiceFactory
{
    private DataServiceFactory()
    {
        // No instantiation allowed!
    }

    public static IDataService GetDataService()
    {
        string sServiceSetting = 
            ConfigurationSettings.AppSettings["dataservice"];
        string[] availableServices = sServiceSetting.Split(',');
        IDataService dataService = null;

        // We try all services until we find a valid one
        foreach (string service in availableServices)
        {
            switch (service)
            {
                case "sqlserver":
                    dataService = new SqlServerDataService();
                    if (dataService.IsValid())
                    {
                        return dataService;
                    }
                    break;
                case "webservice":
                    dataService = new SqlWebDataService();
                    if (dataService.IsValid())
                    {
                        return dataService;
                    }
                    break;
            }
        }

        return dataService;
    }
}