PerRequest.cs

[AttributeUsage(AttributeTargets.Class, AllowMultiple = false, Inherited = true)]
public class PerRequestAttribute : Attribute
{
}

reg1.cs

container.PerRequest<MainViewModel>():
container.PerRequest<AboutViewModel>();

container.Singleton<SessionService>();
container.RegisterSingleton(typeof(ISettingsService),null,typeof(SettingsService));

reg2.cs

// Automatically registers all view models and services
foreach (var type in (typeof(MainViewModel).GetTypeInfo().Assembly.DefinedTypes)
    .Union((typeof(ContactPointsService).GetTypeInfo().Assembly.DefinedTypes)))
{
    if (type.IsClass && !type.IsAbstract)
    {
        // Non-inherited first, inherited second
        if (type.GetCustomAttributes(inherit: false).OfType<SingletonAttribute>().Any())
        {
            container.RegisterSingleton(type.ImplementedInterfaces.Count()==1 ? type.ImplementedInterfaces.First() : type.AsType(), null, type.AsType());
        }
        else if (type.GetCustomAttributes(inherit: false).OfType<PerRequestAttribute>().Any())
        {
            container.RegisterPerRequest(type.ImplementedInterfaces.Count()==1 ? type.ImplementedInterfaces.First() : type.AsType(), null, type.AsType());
        }
        else if (type.GetCustomAttributes(inherit: true).OfType<SingletonAttribute>().Any())
        {
            container.RegisterSingleton(type.ImplementedInterfaces.Count() == 1 ? type.ImplementedInterfaces.First() : type.AsType(), null, type.AsType());
        }
        else if (type.GetCustomAttributes(inherit: true).OfType<PerRequestAttribute>().Any())
        {
            container.RegisterPerRequest(type.ImplementedInterfaces.Count() == 1 ? type.ImplementedInterfaces.First() : type.AsType(), null, type.AsType());
        }                     
    }
}       

reg3.cs

// Automatically registers all types from the current assembly that have correct attribute
foreach (var type in (Assembly.GetExecutingAssembly().GetTypes())
  .Union(Assembly.Load("business logic assembly name").GetTypes()))
{
    if (type.IsClass && !type.IsAbstract)
    {
        var interfaces = type.GetInterfaces();

        // Non-inherited first, inherited second
        if (type.GetCustomAttributes(inherit: false).OfType<SingletonAttribute>().Any())
        {
            container.RegisterSingleton(interfaces.Count() == 1 ? interfaces.First() : type, null, type);
        }
        else if (type.GetCustomAttributes(inherit: false).OfType<PerRequestAttribute>().Any())
        {
            container.RegisterPerRequest(interfaces.Count()==1 ? interfaces.First() : type, null, type);
        }
        else if (type.GetCustomAttributes(inherit: true).OfType<SingletonAttribute>().Any())
        {
            container.RegisterSingleton(interfaces.Count() == 1 ? interfaces.First() : type, null, type);
        }
        else if (type.GetCustomAttributes(inherit: true).OfType<PerRequestAttribute>().Any())
        {
            container.RegisterPerRequest(interfaces.Count() == 1 ? interfaces.First() : type, null, type);
        }
    }
}       

Singleton.cs

[AttributeUsage(AttributeTargets.Class, AllowMultiple = false, Inherited = true)]
public class SingletonAttribute : Attribute
{
}