complete account page

Billing.Shared/UI/Definition.cs

@@ -1,4 +1,8 @@
 using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Xml.Linq;
+using Billing.Models;
 using Xamarin.Forms;
 
 namespace Billing.UI
@@ -75,6 +79,51 @@ namespace Billing.UI
         }
     }
 
+    public static class ModelExtensionHelper
+    {
+        public static List<T> FromStream<T>(Stream stream) where T : IModel, new()
+        {
+            XDocument doc = XDocument.Load(stream);
+            var root = doc.Root;
+            var list = new List<T>();
+            foreach (XElement ele in root.Elements("item"))
+            {
+                if (ele.Attribute("null")?.Value == "1")
+                {
+                    list.Add(default);
+                }
+                else
+                {
+                    T value = new();
+                    value.OnXmlDeserialize(ele);
+                    list.Add(value);
+                }
+            }
+            return list;
+        }
+
+        public static void ToStream<T>(this IEnumerable<T> list, Stream stream) where T : IModel
+        {
+            XElement root = new("root");
+            foreach (var t in list)
+            {
+                XElement item = new("item");
+                if (t == null)
+                {
+                    item.Add(new XAttribute("null", 1));
+                }
+                else
+                {
+                    t.OnXmlSerialize(item);
+                }
+                root.Add(item);
+            }
+
+            XDocument doc = new(new XDeclaration("1.0", "utf-8", "yes"), root);
+            doc.Save(stream, SaveOptions.DisableFormatting);
+        }
+    }
+
     public class Tap : IDisposable
     {
         private readonly static object sync = new();