First day

Exercise1/StoreData/IShoppingCart.cs

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+using System.Collections.Generic;
+
+namespace StoreData
+{
+    public interface IShoppingCart
+    {
+        /// <summary>
+        /// This method adds a product to the shopping cart
+        /// </summary>
+        /// <param name="p">The product to add</param>
+        void AddProduct(Product p);
+
+        /// <summary>
+        /// Remove product by number
+        /// </summary>
+        /// <param name="index">The index of the product to remove</param>
+        void RemoveProductByNumber(int index);
+
+        /// <summary>
+        /// Clears the entire shopping cart
+        /// </summary>
+        void Clear();
+
+        /// <summary>
+        /// Calculate the sum of the cost of all products
+        /// </summary>
+        /// <returns></returns>
+        decimal TotalSum();
+
+        /// <summary>
+        /// Returns true if cart is empty, otherwise false
+        /// </summary>
+        bool CartIsEmpty();
+
+        List<Product> Products { get; }
+    }
+}