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var twoService = ServiceDescriptor.Describe(typeof(ITwoService), typeof(TwoService), ServiceLifetime.Scoped);
services.Add(twoService);

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var threeService = ServiceDescriptor.Scoped(typeof(IThreeService), typeof(ThreeService));
services.Add(threeService);

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var fourService = ServiceDescriptor.Scoped<IFourService, FourService>();
services.Add(fourService);

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services.Replace(ServiceDescriptor.Scoped<IFourService, FourService>());

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services.TryAddEnumerable(ServiceDescriptor.Scoped<IThreeService, ThreeService>());
// or
services.TryAddEnumerable(new[] {
    ServiceDescriptor.Scoped<IThreeService, ThreeService>(),
    ServiceDescriptor.Scoped<IThreeService, AwesomeThreeService>(),
    ServiceDescriptor.Scoped<IThreeService, SuperAwesomeThreeService>()
});

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services.AddScoped<IDiscountProcessor, OrderDiscountProcessor>();
services.AddScoped<IDiscount, SeasonalDiscount>();
services.AddScoped<IDiscount, LargeOrderDiscount>();
services.AddScoped<IDiscount, ThreeOrModeDiscount>(); 

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services.AddScoped<IDiscountProcessor, OrderDiscountProcessor>();
services.TryAddEnumerable(new[]
{
    ServiceDescriptor.Scoped<IDiscount, SeasonalDiscount>(),
    ServiceDescriptor.Scoped<IDiscount, LargeOrderDiscount>(),
    ServiceDescriptor.Scoped<IDiscount, ThreeOrModeDiscount>()
});

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public class OrderDiscountProcessor : IDiscountProcessor
{
    private readonly IEnumerable<IDiscount> _discounts;

    public OrderDiscountProcessor(IEnumerable<IDiscount> discounts)
    {
        _discounts = discounts;
    }
    // ...
}

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public (double, List<string>) ProcessDiscount(OrderViewModel order)
{
    var discountDiscroptoons = new List<string>();
    var totalDiscount = 0.0;

    foreach (var discount in _discounts)
    {
        var addedDiscount = discount.CalculateDiscount(order);
        if (addedDiscount > 0)
        {

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services.AddScoped<IDiscountProcessor, OrderDiscountProcessor>();
services.AddScoped<Discount>(sp =>
{
    return new DiscountBuilder()
        .WithMinimumBillAmount(1000)
        .WithMinimumItemCount(3)
        .WithPercentage(10)
        .Build();
});