如何:跨应用程序会话保持和还原应用程序范围的属性
此示例演示如何在应用程序关闭时保持应用程序范围的属性,以及当应用程序下一次启动后如何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持到独立存储区中,并从中还原这些属性。 独立存储区是受保护的存储区域,可以安全地供应用程序使用,而不需要文件访问权限。
<Application
xmlns="https://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="https://schemas.microsoft.com/winfx/2006/xaml"
x:Class="SDKSample.App"
StartupUri="MainWindow.xaml"
Startup="App_Startup"
Exit="App_Exit">
...
</Application>
Imports System.IO ' StreamReader, FileMode
Imports System.IO.IsolatedStorage ' IsolatedStorageFile, IsolatedStorageFileStream
Namespace SDKSample
Partial Public Class App
Inherits Application
Private filename As String = "App.txt"
...
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
using System.Windows; // Application, StartupEventArgs
using System.IO; // StreamReader, FileMode
using System.IO.IsolatedStorage; // IsolatedStorageFile, IsolatedStorageFileStream
namespace SDKSample
{
public partial class App : Application
{
string filename = "App.txt";
...
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]);
}
}
}
}
}