WIP creational patterns

creational/builder/FacadeBuilderSample.cs

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+using System;
+using System.Threading.Tasks;
+
+namespace design_patterns.creational.facadebuilder
+{
+    /// <summary>
+    /// this sample covers the case when we have multiple builders 
+    /// for the same class, that we want to chain
+    /// </summary>
+    public class FacadeBuilderSample
+    {
+        public static async Task Run() {
+            Console.WriteLine("Creational - Facade Builder");
+
+            var product = new ProductBuilder()
+                .Info
+                    .WithName("New Product")
+                    .WithDetails("product details")
+                .Price
+                    .WithPrice(67.12m)
+                    .WithDiscountLevel1(4)
+                    .WithDiscountLevel2(12)
+                .Build();
+            
+            Console.WriteLine("product: " +  product.ToString());
+
+            // sample with implicit operator casting
+            Product product2 = new ProductBuilder()
+                .Info
+                    .WithName("New Product 2")
+                    .WithDetails("product details 2")
+                .Price
+                    .WithPrice(23.11m)
+                    .WithDiscountLevel1(5)
+                    .WithDiscountLevel2(10);
+            
+            Console.WriteLine("product: " +  product2.ToString());
+        }
+    }
+
+    public class Product {
+        // first section handled by a builder
+        public string Name { get; set; }
+        public string Details { get; set; }
+
+        // second section handled by another builder
+        public decimal Price { get; set; }
+        public int DiscountPercentLevel1 { get; set; }
+        public int DiscountPercentLevel2 { get; set; }
+        
+
+        public override string ToString()
+        {
+            return $"{Name} : {Details} : {Price} : {DiscountPercentLevel1} : {DiscountPercentLevel2}";
+        }
+    }
+
+    // this acts as a facade
+    public class ProductBuilder
+    {
+        protected Product instance = new Product();
+
+        public ProductInfoBuilder Info => new ProductInfoBuilder(instance);
+        public ProductPriceBuilder Price => new ProductPriceBuilder(instance);
+
+        public Product Build() {
+            return instance;
+        }
+
+        public static implicit operator Product(ProductBuilder pb) => pb.instance;
+    }
+
+    public class ProductInfoBuilder : ProductBuilder {
+        public ProductInfoBuilder(Product instance) {
+            this.instance = instance;
+        }
+
+        public ProductInfoBuilder WithName(string name) {
+            this.instance.Name = name;
+            return this;
+        }
+
+        public ProductInfoBuilder WithDetails(string details) {
+            this.instance.Details = details;
+            return this;
+        }
+    }
+
+    public class ProductPriceBuilder : ProductBuilder {
+        public ProductPriceBuilder(Product instance) {
+            this.instance = instance;
+        }
+
+        public ProductPriceBuilder WithPrice(decimal price) {
+            this.instance.Price = price;
+            return this;
+        }
+
+        public ProductPriceBuilder WithDiscountLevel1(int discount) {
+            this.instance.DiscountPercentLevel1 = discount;
+            return this;
+        }
+
+        public ProductPriceBuilder WithDiscountLevel2(int discount) {
+            this.instance.DiscountPercentLevel2 = discount;
+            return this;
+        }
+    }
+}