/// <summary>
 /// Extension mechanism for additional services;  
 /// </summary>
 /// <returns>requested service provider or null.</returns>
 object IServiceProvider.GetService(Type serviceType) {
     object result = null;
     if (serviceType == typeof(DbProviderServices)) {
         result = EntityProviderServices.Instance;
     }
     else if (serviceType == typeof(IEntityAdapter)) {
         result = new EntityAdapter();
     }
     return result;
 }