Update persistent storage example for WPF Framework (#1856)

* Update example * cull some needless comments
dotnet · Jun 14, 2024 · ec78e78 · ec78e78
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diff --git a/...amework/wpf/app-development/persist-and-restore-application-scope-properties.md b/...amework/wpf/app-development/persist-and-restore-application-scope-properties.md
@@ -1,7 +1,7 @@
 ---
 title: "How to: Persist and Restore Application-Scope Properties Across Application Sessions"
 description: Learn how to persist and restore application-scope properties across application sessions via included code examples in XAML, C#, and Visual Basic.
-ms.date: "03/30/2017"
+ms.date: 06/13/2024
 dev_langs: 
   - "csharp"
   - "vb"
@@ -18,11 +18,17 @@ ms.assetid: 55d5904a-f444-4eb5-abd3-6bc74dd14226
 
 This example shows how to persist application-scope properties when an application shuts down, and how to restore application-scope properties when an application is next launched.
 
-## Example  
+## Example
 
- The application persists application-scope properties to, and restores them from, isolated storage. Isolated storage is a protected storage area that can safely be used by applications without file access permission.  The *App.xaml* file defines the `App_Startup` method as the handler for the <xref:System.Windows.Application.Startup?displayProperty=nameWithType> event, and the `App_Exit` method as the handler for the  <xref:System.Windows.Application.Exit?displayProperty=nameWithType> event, as shown in the highlighted lines of the first example. The second example shows a portion of the *App.xaml.cs* and *App.xaml.vb* files that highlights the code for the `App_Startup` method, which restores application-scope properties, and the `App_Exit` method, which saves application-scope properties.
+The application persists application-scope properties to, and restores them from, isolated storage. Isolated storage is a protected storage area that can safely be used by applications without file access permission. The *App.xaml* file defines the `App_Startup` method as the handler for the <xref:System.Windows.Application.Startup?displayProperty=nameWithType> event, and the `App_Exit` method as the handler for the <xref:System.Windows.Application.Exit?displayProperty=nameWithType> event, as shown in the highlighted lines of the following XAML:
 
- [!code-xaml[HOWTOApplicationModelSnippets#PersistRestoreAppScopePropertiesXAML1](~/samples/snippets/csharp/VS_Snippets_Wpf/HOWTOApplicationModelSnippets/CSharp/App.xaml?highlight=1-7)]
-
- [!code-csharp[HOWTOApplicationModelSnippets#PersistRestoreAppScopePropertiesCODEBEHIND1](~/samples/snippets/csharp/VS_Snippets_Wpf/HOWTOApplicationModelSnippets/CSharp/App.xaml.cs?highlight=17-55)]
- [!code-vb[HOWTOApplicationModelSnippets#PersistRestoreAppScopePropertiesCODEBEHIND1](~/samples/snippets/visualbasic/VS_Snippets_Wpf/HOWTOApplicationModelSnippets/visualbasic/application.xaml.vb?highlight=14-45)]
+> [!NOTE]
+> The following XAML is written for CSharp. The Visual Basic version omits the class declaration.
+
+:::code language="xaml" source="./snippets/persist-and-restore-application-scope-properties/csharp/App.xaml" highlight="5,6":::
+
+This next example shows the Application code-behind, which contains the event handlers for the XAML. The `App_Startup` method restores application-scope properties, and the `App_Exit` method saves application-scope properties.
+
+:::code language="csharp" source="./snippets/persist-and-restore-application-scope-properties/csharp/App.xaml.cs":::
+
+:::code language="vb" source="./snippets/persist-and-restore-application-scope-properties/vb/Application.xaml.vb":::
diff --git a/...app-development/snippets/persist-and-restore-application-scope-properties/csharp/App.xaml b/...app-development/snippets/persist-and-restore-application-scope-properties/csharp/App.xaml
@@ -0,0 +1,7 @@
+<Application x:Class="SDKSamples.App"
+             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             StartupUri="MainWindow.xaml"
+             Startup="App_Startup"
+             Exit="App_Exit">
+</Application>
diff --git a/...-development/snippets/persist-and-restore-application-scope-properties/csharp/App.xaml.cs b/...-development/snippets/persist-and-restore-application-scope-properties/csharp/App.xaml.cs
@@ -0,0 +1,66 @@
+using System.IO.IsolatedStorage;
+using System.IO;
+using System.Windows;
+
+namespace SDKSamples
+{
+    public partial class App : Application
+    {
+        string _filename = "App.data";
+
+        public App()
+        {
+            // Initialize application-scope property
+            Properties["NumberOfAppSessions"] = "0";
+        }
+
+        private void App_Startup(object sender, StartupEventArgs e)
+        {
+            // Restore application-scope property from isolated storage
+            IsolatedStorageFile storage = IsolatedStorageFile.GetUserStoreForDomain();
+            try
+            {
+                if (storage.FileExists(_filename))
+                {
+                    using (IsolatedStorageFileStream stream = storage.OpenFile(_filename, FileMode.Open, FileAccess.Read))
+                    using (StreamReader reader = new StreamReader(stream))
+                    {
+                        // Restore each application-scope property individually
+                        while (!reader.EndOfStream)
+                        {
+                            string[] keyValue = reader.ReadLine().Split(new char[] { ',' });
+                            Properties[keyValue[0]] = keyValue[1];
+                        }
+                    }
+                }
+            }
+            catch (DirectoryNotFoundException ex)
+            {
+                // Path the file didn't exist
+            }
+            catch (IsolatedStorageException ex)
+            {
+                // Storage was removed or doesn't exist
+                // -or-
+                // If using .NET 6+ the inner exception contains the real cause
+            }
+        }
+
+        private void App_Exit(object sender, ExitEventArgs e)
+        {
+            // Increase the amount of times the app was opened
+            Properties["NumberOfAppSessions"] = int.Parse((string)Properties["NumberOfAppSessions"]) + 1;
+
+            // Persist application-scope property to isolated storage
+            IsolatedStorageFile storage = IsolatedStorageFile.GetUserStoreForDomain();
+            using (IsolatedStorageFileStream stream = storage.OpenFile(_filename, FileMode.Create, FileAccess.Write))
+            using (StreamWriter writer = new StreamWriter(stream))
+            {
+                // Persist each application-scope property individually
+                foreach (string key in Properties.Keys)
+                    writer.WriteLine("{0},{1}", key, Properties[key]);
+            }
+        }
+    }
+
+}
diff --git a/...elopment/snippets/persist-and-restore-application-scope-properties/csharp/AssemblyInfo.cs b/...elopment/snippets/persist-and-restore-application-scope-properties/csharp/AssemblyInfo.cs
@@ -0,0 +1,10 @@
+using System.Windows;
+
+[assembly:ThemeInfo(
+    ResourceDictionaryLocation.None,            //where theme specific resource dictionaries are located
+                                                //(used if a resource is not found in the page,
+                                                // or application resource dictionaries)
+    ResourceDictionaryLocation.SourceAssembly   //where the generic resource dictionary is located
+                                                //(used if a resource is not found in the page,
+                                                // app, or any theme specific resource dictionaries)
+)]
diff --git a/...elopment/snippets/persist-and-restore-application-scope-properties/csharp/MainWindow.xaml b/...elopment/snippets/persist-and-restore-application-scope-properties/csharp/MainWindow.xaml
@@ -0,0 +1,14 @@
+<Window x:Class="SDKSamples.MainWindow"
+        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+        xmlns:local="clr-namespace:SDKSamples"
+        mc:Ignorable="d"
+        Title="MainWindow" Height="450" Width="800" Loaded="Window_Loaded">
+    <Grid>
+        <Label Content="Times app was opened: " HorizontalAlignment="Left" Margin="31,80,0,0" VerticalAlignment="Top"/>
+        <Label Content="X" HorizontalAlignment="Left" Margin="168,80,0,0" VerticalAlignment="Top" x:Name="lblTimes"/>
+
+    </Grid>
+</Window>
diff --git a/...pment/snippets/persist-and-restore-application-scope-properties/csharp/MainWindow.xaml.cs b/...pment/snippets/persist-and-restore-application-scope-properties/csharp/MainWindow.xaml.cs
@@ -0,0 +1,32 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Data;
+using System.Windows.Documents;
+using System.Windows.Input;
+using System.Windows.Media;
+using System.Windows.Media.Imaging;
+using System.Windows.Shapes;
+
+namespace SDKSamples
+{
+    /// <summary>
+    /// Interaction logic for MainWindow.xaml
+    /// </summary>
+    public partial class MainWindow : Window
+    {
+        public MainWindow()
+        {
+            InitializeComponent();
+        }
+
+        private void Window_Loaded(object sender, RoutedEventArgs e)
+        {
+            lblTimes.Content = App.Current.Properties["NumberOfAppSessions"];
+        }
+    }
+}
diff --git a/...lopment/snippets/persist-and-restore-application-scope-properties/csharp/ProjectCS.csproj b/...lopment/snippets/persist-and-restore-application-scope-properties/csharp/ProjectCS.csproj
@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>WinExe</OutputType>
+    <TargetFramework>net481</TargetFramework>
+    <UseWPF>true</UseWPF>
+    <RootNamespace>SDKSamples</RootNamespace>
+    <ApplicationManifest>app.manifest</ApplicationManifest>
+  </PropertyGroup>
+
+</Project>
diff --git a/...development/snippets/persist-and-restore-application-scope-properties/csharp/app.manifest b/...development/snippets/persist-and-restore-application-scope-properties/csharp/app.manifest
@@ -0,0 +1,77 @@
+<?xml version="1.0" encoding="utf-8"?>
+<assembly manifestVersion="1.0" xmlns="urn:schemas-microsoft-com:asm.v1">
+  <assemblyIdentity version="1.0.0.0" name="MyApplication.app"/>
+  <trustInfo xmlns="urn:schemas-microsoft-com:asm.v2">
+    <security>
+      <requestedPrivileges xmlns="urn:schemas-microsoft-com:asm.v3">
+        <!-- UAC Manifest Options
+             If you want to change the Windows User Account Control level replace the 
+             requestedExecutionLevel node with one of the following.
+
+        <requestedExecutionLevel  level="asInvoker" uiAccess="false" />
+        <requestedExecutionLevel  level="requireAdministrator" uiAccess="false" />
+        <requestedExecutionLevel  level="highestAvailable" uiAccess="false" />
+
+            Specifying requestedExecutionLevel element will disable file and registry virtualization. 
+            Remove this element if your application requires this virtualization for backwards
+            compatibility.
+        -->
+        <requestedExecutionLevel level="asInvoker" uiAccess="false" />
+      </requestedPrivileges>
+    </security>
+  </trustInfo>
+
+  <compatibility xmlns="urn:schemas-microsoft-com:compatibility.v1">
+    <application>
+      <!-- A list of the Windows versions that this application has been tested on
+           and is designed to work with. Uncomment the appropriate elements
+           and Windows will automatically select the most compatible environment. -->
+
+      <!-- Windows Vista -->
+      <!--<supportedOS Id="{e2011457-1546-43c5-a5fe-008deee3d3f0}" />-->
+
+      <!-- Windows 7 -->
+      <!--<supportedOS Id="{35138b9a-5d96-4fbd-8e2d-a2440225f93a}" />-->
+
+      <!-- Windows 8 -->
+      <!--<supportedOS Id="{4a2f28e3-53b9-4441-ba9c-d69d4a4a6e38}" />-->
+
+      <!-- Windows 8.1 -->
+      <!--<supportedOS Id="{1f676c76-80e1-4239-95bb-83d0f6d0da78}" />-->
+
+      <!-- Windows 10 -->
+      <!--<supportedOS Id="{8e0f7a12-bfb3-4fe8-b9a5-48fd50a15a9a}" />-->
+
+    </application>
+  </compatibility>
+
+  <!-- Indicates that the application is DPI-aware and will not be automatically scaled by Windows at higher
+       DPIs. Windows Presentation Foundation (WPF) applications are automatically DPI-aware and do not need 
+       to opt in. Windows Forms applications targeting .NET Framework 4.6 that opt into this setting, should 
+       also set the 'EnableWindowsFormsHighDpiAutoResizing' setting to 'true' in their app.config. 
+       
+       Makes the application long-path aware. See https://docs.microsoft.com/windows/win32/fileio/maximum-file-path-limitation -->
+  <!--
+  <application xmlns="urn:schemas-microsoft-com:asm.v3">
+    <windowsSettings>
+      <dpiAware xmlns="http://schemas.microsoft.com/SMI/2005/WindowsSettings">true</dpiAware>
+      <longPathAware xmlns="http://schemas.microsoft.com/SMI/2016/WindowsSettings">true</longPathAware>
+    </windowsSettings>
+  </application>
+  -->
+
+  <!-- Enable themes for Windows common controls and dialogs (Windows XP and later) -->
+  <dependency>
+    <dependentAssembly>
+      <assemblyIdentity
+          type="win32"
+          name="Microsoft.Windows.Common-Controls"
+          version="6.0.0.0"
+          processorArchitecture="*"
+          publicKeyToken="6595b64144ccf1df"
+          language="*"
+        />
+    </dependentAssembly>
+  </dependency>
+
+</assembly>
diff --git a/...f/app-development/snippets/persist-and-restore-application-scope-properties/vb/App.config b/...f/app-development/snippets/persist-and-restore-application-scope-properties/vb/App.config
@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<configuration>
+    <startup> 
+        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.8.1" />
+    </startup>
+</configuration>
diff --git a/...development/snippets/persist-and-restore-application-scope-properties/vb/Application.xaml b/...development/snippets/persist-and-restore-application-scope-properties/vb/Application.xaml
@@ -0,0 +1,7 @@
+<Application x:Class="Application"
+             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             StartupUri="MainWindow.xaml"
+             Startup="App_Startup"
+             Exit="App_Exit">
+</Application>
diff --git a/...elopment/snippets/persist-and-restore-application-scope-properties/vb/Application.xaml.vb b/...elopment/snippets/persist-and-restore-application-scope-properties/vb/Application.xaml.vb
@@ -0,0 +1,61 @@
+Imports System.IO
+Imports System.IO.IsolatedStorage
+
+Class Application
+
+    Private _filename As String = "App.data"
+
+    Public Sub New()
+        ' Initialize application-scope property
+        Properties("NumberOfAppSessions") = "0"
+    End Sub
+
+    Private Sub App_Startup(ByVal sender As Object, ByVal e As StartupEventArgs)
+        ' Restore application-scope property from isolated storage
+        Dim storage As IsolatedStorageFile = IsolatedStorageFile.GetUserStoreForDomain()
+        Try
+            If storage.FileExists(_filename) Then
+
+                Using stream As IsolatedStorageFileStream = storage.OpenFile(_filename, FileMode.Open, FileAccess.Read)
+                    Using reader As New StreamReader(stream)
+
+                        ' Restore each application-scope property individually
+                        Do While Not reader.EndOfStream
+                            Dim keyValue() As String = reader.ReadLine().Split(New Char() {","c})
+                            Properties(keyValue(0)) = keyValue(1)
+                        Loop
+
+                    End Using
+                End Using
+
+            End If
+
+        Catch ex As DirectoryNotFoundException
+            ' Path the file didn't exist
+        Catch ex As IsolatedStorageException
+            ' Storage was removed or doesn't exist
+            ' -or-
+            ' If using .NET 6+ the inner exception contains the real cause
+        End Try
+    End Sub
+
+    Private Sub App_Exit(ByVal sender As Object, ByVal e As ExitEventArgs)
+        'Increase the amount of times the app was opened
+        Properties("NumberOfAppSessions") = Integer.Parse(DirectCast(Properties("NumberOfAppSessions"), String)) + 1
+
+        ' Persist application-scope property to isolated storage
+        Dim storage As IsolatedStorageFile = IsolatedStorageFile.GetUserStoreForDomain()
+
+        Using stream As IsolatedStorageFileStream = storage.OpenFile(_filename, FileMode.Create, FileAccess.Write)
+            Using writer As New StreamWriter(stream)
+
+                ' Persist each application-scope property individually
+                For Each key As String In Properties.Keys
+                    writer.WriteLine("{0},{1}", key, Properties(key))
+                Next key
+
+            End Using
+        End Using
+    End Sub
+
+End Class
diff --git a/...-development/snippets/persist-and-restore-application-scope-properties/vb/AssemblyInfo.vb b/...-development/snippets/persist-and-restore-application-scope-properties/vb/AssemblyInfo.vb
@@ -0,0 +1,11 @@
+Imports System.Windows
+
+'The ThemeInfo attribute describes where any theme specific and generic resource dictionaries can be found.
+'1st parameter: where theme specific resource dictionaries are located
+'(used if a resource is not found in the page,
+' or application resource dictionaries)
+
+'2nd parameter: where the generic resource dictionary is located
+'(used if a resource is not found in the page,
+'app, and any theme specific resource dictionaries)
+<Assembly: ThemeInfo(ResourceDictionaryLocation.None, ResourceDictionaryLocation.SourceAssembly)>
diff --git a/...-development/snippets/persist-and-restore-application-scope-properties/vb/MainWindow.xaml b/...-development/snippets/persist-and-restore-application-scope-properties/vb/MainWindow.xaml
@@ -0,0 +1,14 @@
+<Window x:Class="MainWindow"
+        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+        xmlns:local="clr-namespace:SDKSamples"
+        mc:Ignorable="d"
+        Title="MainWindow" Height="450" Width="800"
+        Loaded="Window_Loaded">
+    <Grid>
+        <Label Content="Times app was opened: " HorizontalAlignment="Left" Margin="15,376,0,0" VerticalAlignment="Top"/>
+        <Label Content="X" HorizontalAlignment="Left" Margin="152,376,0,0" VerticalAlignment="Top" x:Name="lblTimes"/>
+    </Grid>
+</Window>
diff --git a/...velopment/snippets/persist-and-restore-application-scope-properties/vb/MainWindow.xaml.vb b/...velopment/snippets/persist-and-restore-application-scope-properties/vb/MainWindow.xaml.vb
@@ -0,0 +1,5 @@
+Public Class MainWindow
+    Private Sub Window_Loaded(sender As Object, e As RoutedEventArgs)
+        lblTimes.Content = Application.Current.Properties("NumberOfAppSessions")
+    End Sub
+End Class