From aa49052a81854b349fa72e34fc3fc74bed896ae0 Mon Sep 17 00:00:00 2001
From: Jason Zhu <jasonzhuyq@outlook.com>
Date: Mon, 5 Jul 2021 18:21:52 +1000
Subject: [PATCH] 5.1.3 Using Extension Methods

---
 .../essential_csharp_features/Product.cs      | 18 +++++++
 .../essential_csharp_features/Program.cs      | 47 ++++++++++---------
 .../essential_csharp_features/ShoppingCart.cs |  9 ++++
 3 files changed, 51 insertions(+), 23 deletions(-)
 create mode 100644 chap5_essential_language_features/essential_csharp_features/Product.cs
 create mode 100644 chap5_essential_language_features/essential_csharp_features/ShoppingCart.cs

diff --git a/chap5_essential_language_features/essential_csharp_features/Product.cs b/chap5_essential_language_features/essential_csharp_features/Product.cs
new file mode 100644
index 0000000..e5f628e
--- /dev/null
+++ b/chap5_essential_language_features/essential_csharp_features/Product.cs
@@ -0,0 +1,18 @@
+namespace automatically_implemented_properties
+{
+    public class Product
+    {
+        private string name;
+        
+        public int ProductID { get; set; }
+
+        public string Name
+        {
+            get { return ProductID + name; }
+            set { name = value; }
+        }
+        public string Description { get; set; }
+        public decimal Price { get; set; }
+        public string Category { set; get; }
+    }
+}
\ No newline at end of file
diff --git a/chap5_essential_language_features/essential_csharp_features/Program.cs b/chap5_essential_language_features/essential_csharp_features/Program.cs
index d58a988..e8c0b0c 100644
--- a/chap5_essential_language_features/essential_csharp_features/Program.cs
+++ b/chap5_essential_language_features/essential_csharp_features/Program.cs
@@ -1,5 +1,7 @@
 using System;
+using System.Collections.Generic;
 using System.Diagnostics;
+using automatically_implemented_properties;
 
 namespace automatically_implemented_properties
 {
@@ -7,36 +9,35 @@ namespace automatically_implemented_properties
     {
         static void Main(string[] args)
         {
-            //  create a new Product object and use method on it
-            ProcessProduct(new Product
+            // create and populate Shopping Cart
+            ShoppingCart cart = new ShoppingCart
             {
-                ProductID = 100,
-                Name = "Kayak",
-                Description = "A boat for one person",
-                Price = 275M,
-                Category = "Watersports"
-            });
+                Products = new List<Product>
+                {
+                    new Product {Name = "Kayak", Price = 275M},
+                    new Product {Name = "Lifejacket", Price = 48.95M},
+                    new Product {Name = "Soccer ball", Price = 19.50M},
+                    new Product {Name = "Corner flag", Price = 34.95M}
+                }
+            };
+            // get total value of the products in cart
+            decimal cartTotal = cart.TotalPrices();
+            
+            Console.WriteLine("Total: {0:c}", cartTotal);
         }
 
-        private static void ProcessProduct(Product prodParam)
-        {
-            // ... statements to process product in some way
-        }
     }
 
-    public class Product
+    public static class MyExtensionMethod
     {
-        private string name;
-        
-        public int ProductID { get; set; }
-
-        public string Name
+        public static decimal TotalPrices(this ShoppingCart cartParam)
         {
-            get { return ProductID + name; }
-            set { name = value; }
+            decimal total = 0;
+            foreach (Product prod in cartParam.Products)
+            {
+                total += prod.Price;
+            }
+            return total;
         }
-        public string Description { get; set; }
-        public decimal Price { get; set; }
-        public string Category { set; get; }
     }
 }
\ No newline at end of file
diff --git a/chap5_essential_language_features/essential_csharp_features/ShoppingCart.cs b/chap5_essential_language_features/essential_csharp_features/ShoppingCart.cs
new file mode 100644
index 0000000..428301f
--- /dev/null
+++ b/chap5_essential_language_features/essential_csharp_features/ShoppingCart.cs
@@ -0,0 +1,9 @@
+using System.Collections.Generic;
+
+namespace automatically_implemented_properties
+{
+    public class ShoppingCart
+    {
+        public List<Product> Products { get; set; }
+    }
+}
\ No newline at end of file