JewelryStoreFileImplement/Class1.cs

@@ -1,7 +0,0 @@
-namespace JewelryStoreFileImplement
-{
-    public class Class1
-    {
-
-    }
-}

JewelryStoreFileImplement/DataFileSingleton.cs

@@ -0,0 +1,62 @@
+using JewelryStoreFileImplement.Models;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.Xml.Linq;
+
+namespace JewelryStoreFileImplement
+{
+    public class DataFileSingleton
+    {
+        private static DataFileSingleton? instance;
+        private readonly string ComponentFileName = "Component.xml";
+        private readonly string OrderFileName = "Order.xml";
+        private readonly string ProductFileName = "Product.xml";
+        public List<Component> Components { get; private set; }
+        public List<Order> Orders { get; private set; }
+        public List<Jewel> Products { get; private set; }
+        public static DataFileSingleton GetInstance()
+        {
+            if (instance == null)
+            {
+                instance = new DataFileSingleton();
+            }
+            return instance;
+        }
+        public void SaveComponents() => SaveData(Components, ComponentFileName,
+"Components", x => x.GetXElement);
+        public void SaveProducts() => SaveData(Products, ProductFileName,
+       "Products", x => x.GetXElement);
+        public void SaveOrders() => SaveData(Orders, OrderFileName, "Orders", x
+       => x.GetXElement);
+        private DataFileSingleton()
+        {
+            Components = LoadData(ComponentFileName, "Component", x =>
+           Component.Create(x)!)!;
+            Products = LoadData(ProductFileName, "Product", x =>
+           Product.Create(x)!)!;
+            Orders = LoadData(OrderFileName, "Order", x => Order.Create(x)!)!;
+        }
+        private static List<T>? LoadData<T>(string filename, string xmlNodeName,
+       Func<XElement, T> selectFunction)
+        {
+            if (File.Exists(filename))
+            {
+                return
+               XDocument.Load(filename)?.Root?.Elements(xmlNodeName)?.Select(selectFunction)?.ToList();
+            }
+            return new List<T>();
+        }
+        private static void SaveData<T>(List<T> data, string filename, string
+       xmlNodeName, Func<T, XElement> selectFunction)
+        {
+            if (data != null)
+            {
+                new XDocument(new XElement(xmlNodeName,
+               data.Select(selectFunction).ToArray())).Save(filename);
+            }
+        }
+    }
+}

JewelryStoreFileImplement/Models/Component.cs

@@ -8,7 +8,7 @@ using System.Text;
 using System.Threading.Tasks;
 using System.Xml.Linq;
 
-namespace JewelryStoreFieImplement.Models
+namespace JewelryStoreFileImplement.Models
 {
     public class Component : IComponentModel
     {