如何:跨应用程序会话保持和还原应用程序范围的属性
此示例演示了如何在应用程序关闭时保留应用程序范围的属性,以及如何在应用程序下次启动时还原应用程序范围的属性。
示例
应用程序将应用程序范围的属性保存到独立存储中,并从中还原这些属性。 独立存储是一个受保护的存储区域,可以安全地供应用程序使用,无需文件访问权限。 App.xaml 文件将 App_Startup
方法定义为 Application.Startup 事件的处理程序,并将 App_Exit
方法定义为 Application.Exit 事件的处理程序,如第一个示例的突出显示行所示。 第二个示例显示了 App.xaml.cs 和 App.xaml.vb 文件的一部分,其中突出显示了 App_Startup
方法(可还原应用程序范围的属性)和 App_Exit
方法(可保存应用程序范围的属性)的代码。
<Application
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
x:Class="SDKSample.App"
StartupUri="MainWindow.xaml"
Startup="App_Startup"
Exit="App_Exit">
<Application.Resources>
<SolidColorBrush x:Key="ApplicationScopeResource" Color="White"></SolidColorBrush>
</Application.Resources>
</Application>
using System.Windows;
using System.IO;
using System.IO.IsolatedStorage;
namespace SDKSample
{
public partial class App : Application
{
string filename = "App.txt";
public App()
{
// Initialize application-scope property
this.Properties["NumberOfAppSessions"] = 0;
}
private void App_Startup(object sender, StartupEventArgs e)
{
// Restore application-scope property from isolated storage
IsolatedStorageFile storage = IsolatedStorageFile.GetUserStoreForDomain();
try
{
using (IsolatedStorageFileStream stream = new IsolatedStorageFileStream(filename, FileMode.Open, storage))
using (StreamReader reader = new StreamReader(stream))
{
// Restore each application-scope property individually
while (!reader.EndOfStream)
{
string[] keyValue = reader.ReadLine().Split(new char[] {','});
this.Properties[keyValue[0]] = keyValue[1];
}
}
}
catch (FileNotFoundException ex)
{
// Handle when file is not found in isolated storage:
// * When the first application session
// * When file has been deleted
}
}
private void App_Exit(object sender, ExitEventArgs e)
{
// Persist application-scope property to isolated storage
IsolatedStorageFile storage = IsolatedStorageFile.GetUserStoreForDomain();
using (IsolatedStorageFileStream stream = new IsolatedStorageFileStream(filename, FileMode.Create, storage))
using (StreamWriter writer = new StreamWriter(stream))
{
// Persist each application-scope property individually
foreach (string key in this.Properties.Keys)
{
writer.WriteLine("{0},{1}", key, this.Properties[key]);
}
}
}
}
}
Imports System.IO
Imports System.IO.IsolatedStorage
Namespace SDKSample
Partial Public Class App
Inherits Application
Private filename As String = "App.txt"
Public Sub New()
' Initialize application-scope property
Me.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
Using stream As New IsolatedStorageFileStream(filename, FileMode.Open, storage)
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})
Me.Properties(keyValue(0)) = keyValue(1)
Loop
End Using
End Using
Catch ex As FileNotFoundException
' Handle when file is not found in isolated storage:
' * When the first application session
' * When file has been deleted
End Try
End Sub
Private Sub App_Exit(ByVal sender As Object, ByVal e As ExitEventArgs)
' Persist application-scope property to isolated storage
Dim storage As IsolatedStorageFile = IsolatedStorageFile.GetUserStoreForDomain()
Using stream As New IsolatedStorageFileStream(filename, FileMode.Create, storage)
Using writer As New StreamWriter(stream)
' Persist each application-scope property individually
For Each key As String In Me.Properties.Keys
writer.WriteLine("{0},{1}", key, Me.Properties(key))
Next key
End Using
End Using
End Sub
End Class
End Namespace
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