/// <summary>
/// Add view model type as singleton service registry.
/// </summary>
/// <typeparam name="T">view model type</typeparam>
/// <param name="serviceRegistry">service registry</param>
/// <param name="transient">register as transient if true; otherwise as singleton</param>
/// <returns>service registry</returns>
public static IServiceRegistry AddViewModel <T>(this IServiceRegistry serviceRegistry, bool transient = false) where T : BaseViewModel
{
var attr = typeof(T).GetTypeInfo().GetCustomAttribute <TransientAttribute>();
transient = attr != null || transient;
return(!transient?serviceRegistry.AddViewModelSingleton <T>() : serviceRegistry.AddViewModelTransient <T>());
}