Gewusst wie: Beibehalten und Wiederherstellen von Eigenschaften für den Anwendungsbereich über mehrere Anwendungssitzungen

In diesem Beispiel wird gezeigt, wie Sie Eigenschaften für den Anwendungsbereich beim Herunterfahren einer Anwendung beibehalten und wie Sie Eigenschaften für den Anwendungsbereich beim nächsten Starten einer Anwendung wiederherstellen.

Beispiel

Die Anwendung enthält Anwendungsbereichseigenschaften, und wiederherstellen Sie sie von isolierten Speicher. Isolierter Speicher ist ein geschützter Speicherbereich, der von Anwendungen ohne Dateizugriffsberechtigung sicher verwendet werden kann. Die Datei App.xaml definiert die App_Startup-Methode als Handler für das Application.Startup-Ereignis und die App_Exit-Methode als Handler für das Application.Exit-Ereignis, wie in den hervorgehobenen Zeilen des folgenden XAML-Codes dargestellt:

<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>

Dieses nächste Beispiel zeigt den Code-Behind der Anwendung, der die Ereignishandler für den XAML-Code enthält. Die App_Startup-Methode stellt Anwendungsbereichseigenschaften wieder her, und die App_Exit-Methode speichert Anwendungsbereichseigenschaften.

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]);
            }
        }
    }

}

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