using System;

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​

namespace TestOptionalNullParameters

{

    public class Product { }

    public class Brand {

        public string BrandProp { get; set; }

    }

​

    public class Program

    {

        static void Main(string[] args)

        {

            Product product = new Product();

            Brand brand = new Brand() { BrandProp = "Set in Main" };

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            Console.WriteLine("Result when calling with GenerateArticle(product, brand):");

            Console.WriteLine("-------------------------------------------------------------------");

            GenerateArticle(product, brand);

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            Console.WriteLine("Result when calling with GenerateArticle(product, null, null):");

            Console.WriteLine("-------------------------------------------------------------------");

            GenerateArticle(product, null);

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            Console.WriteLine("Result when calling with GenerateArticle(product):");

            Console.WriteLine("-------------------------------------------------------------------");

            GenerateArticle(product);

        }

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        public static void GenerateArticle(Product product, Maybe<Brand> maybeBrand = new Maybe<Brand>())

        {

            Brand brand = maybeBrand.IsSet

                ? maybeBrand.Value

                : new Brand() { BrandProp = "Fallback brand" }; // TODO: Proper fallback value

            Console.WriteLine($"product={product} ");

            Console.WriteLine($"brand={brand?.BrandProp} ");

        }

​

        public struct Maybe<T>

        {

            public bool IsSet { get; }

            public T Value { get; }

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            public Maybe(T t)

            {

                IsSet = true;

                Value = t;

            }

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            public Maybe(bool value)

            {

                IsSet = false;

                Value = default(T);

            }

​

            public static implicit operator Maybe<T>(T obj)

            {

                return new Maybe<T>(obj);

            }

        }

​

    }

}

​