SystemEvents 类

定义

public ref class SystemEvents sealed

public sealed class SystemEvents

type SystemEvents = class

Public NotInheritable Class SystemEvents

继承

Object

SystemEvents

示例

本部分包含两个示例。This section contains two examples. 第一个示例演示如何在普通的应用程序中使用系统事件，第二个示例演示如何在 Windows 服务中使用系统事件。The first example shows how to use system events in an ordinary application, and the second example shows how to use system events in a Windows service.

示例1Example 1

下面的代码示例注册了一些系统事件的兴趣，并等待其中任何事件发生。The following code example registers interest in some system events and then waits for any of those events to occur. 如果用户更改了显示分辨率，则会显示输出。The output shown occurs if the user changes the display resolution.

#using <System.dll>

using namespace System;
using namespace Microsoft::Win32;

// This method is called when a user preference changes.
void SystemEvents_UserPreferenceChanging(Object^ sender,
     UserPreferenceChangingEventArgs^ e)
 {
     Console::WriteLine("The user preference is changing. Category={0}",
         e->Category);
 }

// This method is called when the palette changes.
void SystemEvents_PaletteChanged(Object^ sender, EventArgs^ e)
{
    Console::WriteLine("The palette changed.");
}

// This method is called when the display settings change.
void SystemEvents_DisplaySettingsChanged(Object^ sender,
    EventArgs^ e)
{
    Console::WriteLine("The display settings changed.");
}

int main()
{
    // Set the SystemEvents class to receive event notification
    // when a user preference changes, the palette changes, or
    // when display settings change.
    SystemEvents::UserPreferenceChanging += gcnew
        UserPreferenceChangingEventHandler(
        SystemEvents_UserPreferenceChanging);
    SystemEvents::PaletteChanged += gcnew
        EventHandler(SystemEvents_PaletteChanged);
    SystemEvents::DisplaySettingsChanged += gcnew
        EventHandler(SystemEvents_DisplaySettingsChanged);

    // For demonstration purposes, this application sits idle
    // waiting for events.
    Console::WriteLine("This application is waiting for system events.");
    Console::WriteLine("Press <Enter> to terminate this application.");
    Console::ReadLine();
}

// This code produces the following output.
//
//  This app is waiting for system events.
//  Press <Enter> to terminate this application.
//  Display Settings changed.
//  User preference is changing. Category=General

using System;
using Microsoft.Win32;

public sealed class App 
{
    static void Main() 
    {         
        // Set the SystemEvents class to receive event notification when a user 
        // preference changes, the palette changes, or when display settings change.
        SystemEvents.UserPreferenceChanging += new 
            UserPreferenceChangingEventHandler(SystemEvents_UserPreferenceChanging);
        SystemEvents.PaletteChanged += new 
            EventHandler(SystemEvents_PaletteChanged);
        SystemEvents.DisplaySettingsChanged += new 
            EventHandler(SystemEvents_DisplaySettingsChanged);        

        // For demonstration purposes, this application sits idle waiting for events.
        Console.WriteLine("This application is waiting for system events.");
        Console.WriteLine("Press <Enter> to terminate this application.");
        Console.ReadLine();
    }

    // This method is called when a user preference changes.
    static void SystemEvents_UserPreferenceChanging(object sender, UserPreferenceChangingEventArgs e) 
    {
        Console.WriteLine("The user preference is changing. Category={0}", e.Category);
    }

    // This method is called when the palette changes.
    static void SystemEvents_PaletteChanged(object sender, EventArgs e)
    {
        Console.WriteLine("The palette changed.");
    }

    // This method is called when the display settings change.
    static void SystemEvents_DisplaySettingsChanged(object sender, EventArgs e)
    {
        Console.WriteLine("The display settings changed.");
    }
}

// This code produces the following output.
// 
//  This app is waiting for system events.
//  Press <Enter> to terminate this application.
//  Display Settings changed.
//  User preference is changing. Category=General

Imports Microsoft.Win32
Imports System.Windows.Forms

Friend Class Form1
    Inherits System.Windows.Forms.Form


    Public Sub New()
        MyBase.New()

        'This call is required by the Windows Form Designer.
        InitializeComponent()

        'Set the SystemEvents class to receive event notification 
        'when a user preference changes, the palette changes, or 
        'when display settings change.
        AddHandler SystemEvents.UserPreferenceChanging, _
        AddressOf SystemEvents_UserPreferenceChanging

        AddHandler SystemEvents.PaletteChanged, _
        AddressOf SystemEvents_PaletteChanged

        AddHandler SystemEvents.DisplaySettingsChanged, _
        AddressOf SystemEvents_DisplaySettingsChanged

    End Sub

    'Form overrides dispose to clean up the component list.
    Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
        If disposing Then
            If (components IsNot Nothing) Then
                components.Dispose()
            End If
        End If
        MyBase.Dispose(disposing)
    End Sub


    Private components As System.ComponentModel.IContainer

    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()

        Me.SuspendLayout()

        '
        'Form1
        '
        Me.ClientSize = New System.Drawing.Size(648, 398)
        Me.Name = "Form1"
        Me.Text = "Form1"
        Me.ResumeLayout(False)

    End Sub


    ' This method is called when a user preference changes.
    Private Sub SystemEvents_UserPreferenceChanging( _
    ByVal sender As Object, _
    ByVal e As UserPreferenceChangingEventArgs)

        MessageBox.Show("UserPreferenceChanging: " & _
        e.Category.ToString())
    End Sub


    ' This method is called when the palette changes.
    Private Sub SystemEvents_PaletteChanged( _
    ByVal sender As Object, _
    ByVal e As EventArgs)

        MessageBox.Show("PaletteChanged")

    End Sub


    ' This method is called when the display settings change.
    Private Sub SystemEvents_DisplaySettingsChanged( _
    ByVal sender As Object, _
    ByVal e As EventArgs)

        MessageBox.Show("The display settings changed.")

    End Sub

End Class

示例2Example 2

下面的代码示例演示了一个非常简单的 Windows 服务，用于处理 TimeChanged 和 UserPreferenceChanged 事件。The following code example demonstrates a very simple Windows service that handles the TimeChanged and UserPreferenceChanged events. 该示例包括一个名为 SimpleService的服务、一个名为 HiddenForm的窗体和一个安装程序。The example includes a service named SimpleService, a form named HiddenForm, and an installer. 窗体提供系统事件所需的消息循环。The form provides the message loop that is required by system events.

本示例中的服务启动一个线程，该线程运行 HiddenForm的实例。The service in this example starts a thread that runs an instance of HiddenForm. 事件与窗体挂钩并进行处理。The events are hooked up and handled in the form. 必须在窗体的 load 事件中挂接事件，以确保先完全加载窗体;否则，将不会引发事件。The events must be hooked up in the load event of the form, to make sure that the form is completely loaded first; otherwise the events will not be raised.

运行示例：To run the example:

1. 从命令行编译代码。Compile the code from the command line. 用于源文件的名称并不重要。The name that you use for the source file is not important.

2. 在命令行中使用installutil.exe （安装程序工具）实用程序安装服务。Install the service from the command line using the Installutil.exe (Installer Tool) utility. 例如，如果源文件名为 example.cs 或 example.vb，则 InstallUtil example.exe。For example, InstallUtil example.exe if the source file name is example.cs or example.vb. 您必须是管理员才能安装服务。You must be an administrator to install the service.

3. 使用服务控制台启动该服务。Use the Services console to start the service.

4. 更改系统时间或更改用户首选项，例如鼠标属性。Change the system time, or change user preferences, such as mouse properties.

5. 查看事件查看器的应用程序类别中的消息。View the messages in the Application category of Event Viewer.

6. 使用服务控制台停止此服务。Use the Services console to stop the service.

7. 使用 /u 选项从命令行卸载该服务。Uninstall the service from the command line by using the /u option. 例如 InstallUtil /u example.exe。For example, InstallUtil /u example.exe.

using System;
using System.ServiceProcess;
using System.Threading;
using System.Windows.Forms;
using System.Diagnostics;
using Microsoft.Win32;
using System.ComponentModel;
using System.Configuration.Install;

namespace SimpleServiceCs
{
    public class SimpleService : ServiceBase
    {
        static void Main(string[] args)
        {
            ServiceBase.Run(new SimpleService());
        }

        protected override void OnStart(string[] args)
        {
            EventLog.WriteEntry("SimpleService", "Starting SimpleService");
            new Thread(RunMessagePump).Start();
        }

        void RunMessagePump()
        {
            EventLog.WriteEntry("SimpleService.MessagePump", "Starting SimpleService Message Pump");
            Application.Run(new HiddenForm());
        }

        protected override void OnStop()
        {
            Application.Exit();
        }
    }

    public partial class HiddenForm : Form
    {
        public HiddenForm()
        {
            InitializeComponent();
        }

        private void HiddenForm_Load(object sender, EventArgs e)
        {
            SystemEvents.TimeChanged += new EventHandler(SystemEvents_TimeChanged);
            SystemEvents.UserPreferenceChanged += new UserPreferenceChangedEventHandler(SystemEvents_UPCChanged);
        }

        private void HiddenForm_FormClosing(object sender, FormClosingEventArgs e)
        {
            SystemEvents.TimeChanged -= new EventHandler(SystemEvents_TimeChanged);
            SystemEvents.UserPreferenceChanged -= new UserPreferenceChangedEventHandler(SystemEvents_UPCChanged);
        }

        private void SystemEvents_TimeChanged(object sender, EventArgs e)
        {
            EventLog.WriteEntry("SimpleService.TimeChanged", "Time changed; it is now " +
                DateTime.Now.ToLongTimeString());
        }

        private void SystemEvents_UPCChanged(object sender, UserPreferenceChangedEventArgs e)
        {
            EventLog.WriteEntry("SimpleService.UserPreferenceChanged", e.Category.ToString());
        }
    }

    partial class HiddenForm
    {
        private System.ComponentModel.IContainer components = null;

        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        private void InitializeComponent()
        {
            this.SuspendLayout();
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(0, 0);
            this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;
            this.Name = "HiddenForm";
            this.Text = "HiddenForm";
            this.WindowState = System.Windows.Forms.FormWindowState.Minimized;
            this.Load += new System.EventHandler(this.HiddenForm_Load);
            this.FormClosing += new System.Windows.Forms.FormClosingEventHandler(this.HiddenForm_FormClosing);
            this.ResumeLayout(false);

        }
    }

    [RunInstaller(true)]
    public class SimpleInstaller : Installer
    {
        private ServiceInstaller serviceInstaller;
        private ServiceProcessInstaller processInstaller;

        public SimpleInstaller()
        {
            processInstaller = new ServiceProcessInstaller();
            serviceInstaller = new ServiceInstaller();

            // Service will run under system account
            processInstaller.Account = ServiceAccount.LocalSystem;

            // Service will have Start Type of Manual
            serviceInstaller.StartType = ServiceStartMode.Automatic;

            serviceInstaller.ServiceName = "Simple Service";

            Installers.Add(serviceInstaller);
            Installers.Add(processInstaller);
        }
    }
}

Imports System.ServiceProcess
Imports System.Threading
Imports System.Windows.Forms
Imports System.Diagnostics
Imports Microsoft.Win32
Imports System.ComponentModel
Imports System.Configuration.Install

Namespace SimpleServiceVb
    Public Class SimpleService
        Inherits ServiceBase
    
        Shared Sub Main(ByVal args() As String) 
            ServiceBase.Run(New SimpleService())
        End Sub
    
        Protected Overrides Sub OnStart(ByVal args() As String) 
            EventLog.WriteEntry("SimpleService", "Starting SimpleService")
            Dim t As New Thread(AddressOf RunMessagePump)
            t.Start()    
        End Sub
    
        Sub RunMessagePump() 
            EventLog.WriteEntry("SimpleService.MessagePump", _
                "Starting SimpleService Message Pump")
            Application.Run(New HiddenForm())
        End Sub
    
        Protected Overrides Sub OnStop() 
            Application.Exit()
        End Sub
    End Class 

    Partial Class HiddenForm
        Inherits Form

        Public Sub New() 
            InitializeComponent()
        End Sub
    
        Private Sub HiddenForm_Load(ByVal sender As Object, ByVal e As EventArgs) 
            AddHandler SystemEvents.TimeChanged, AddressOf SystemEvents_TimeChanged
            AddHandler SystemEvents.UserPreferenceChanged, AddressOf SystemEvents_UPCChanged
        End Sub 
    
        Private Sub HiddenForm_FormClosing(ByVal sender As Object, ByVal e As FormClosingEventArgs) 
            RemoveHandler SystemEvents.TimeChanged, New EventHandler(AddressOf SystemEvents_TimeChanged)
            RemoveHandler SystemEvents.UserPreferenceChanged, _
                New UserPreferenceChangedEventHandler(AddressOf SystemEvents_UPCChanged)
        End Sub 
    
        Private Sub SystemEvents_TimeChanged(ByVal sender As Object, ByVal e As EventArgs) 
            EventLog.WriteEntry("SimpleService.TimeChanged", _
                "Time changed; it is now " & DateTime.Now.ToLongTimeString())
        End Sub 
    
        Private Sub SystemEvents_UPCChanged(ByVal sender As Object, ByVal e As UserPreferenceChangedEventArgs) 
            EventLog.WriteEntry("SimpleService.UserPreferenceChanged", e.Category.ToString())
        End Sub 
    End Class

    Partial Class HiddenForm

        Private components As System.ComponentModel.IContainer = Nothing
    
        Protected Overrides Sub Dispose(ByVal disposing As Boolean) 
            If disposing AndAlso Not (components Is Nothing) Then
                components.Dispose()
            End If
            MyBase.Dispose(disposing)
        End Sub
  
        Private Sub InitializeComponent() 
            Me.SuspendLayout()
            Me.AutoScaleDimensions = New System.Drawing.SizeF(6F, 13F)
            Me.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font
            Me.ClientSize = New System.Drawing.Size(0, 0)
            Me.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None
            Me.Name = "HiddenForm"
            Me.Text = "HiddenForm"
            Me.WindowState = System.Windows.Forms.FormWindowState.Minimized
            AddHandler Me.Load, AddressOf Me.HiddenForm_Load
            AddHandler Me.FormClosing, AddressOf Me.HiddenForm_FormClosing
            Me.ResumeLayout(False)
        End Sub 
    End Class 

    <RunInstaller(True)> _
    Public Class SimpleInstaller
        Inherits Installer

        Private serviceInstaller As ServiceInstaller
        Private processInstaller As ServiceProcessInstaller
    
        Public Sub New() 
            processInstaller = New ServiceProcessInstaller()
            serviceInstaller = New ServiceInstaller()
        
            ' Service will run under system account
            processInstaller.Account = ServiceAccount.LocalSystem
        
            ' Service will have Start Type of Manual
            serviceInstaller.StartType = ServiceStartMode.Automatic
        
            serviceInstaller.ServiceName = "Simple Service"
        
            Installers.Add(serviceInstaller)
            Installers.Add(processInstaller)
        End Sub
    End Class 
End Namespace

注解

SystemEvents 类提供响应特定类型的系统事件的能力。The SystemEvents class provides the ability to respond to specific types of system events.

引发系统事件时，将使用监视系统事件的线程调用附加到事件的任何委托。When a system event is raised, any delegates attached to the event are called using the thread that monitors for system events. 因此，您应从事件处理程序调用线程安全。Therefore, you should make any calls from your event handlers thread-safe. 如果需要调用未作为此类的成员公开的系统事件，可以使用 InvokeOnEventsThread 方法。If you need to call a system event that is not exposed as a member of this class, you can use the InvokeOnEventsThread method.

方法

事件

安全性

NamedPermissionSet
用于完全访问系统资源。for full access to system resources. 需求值： LinkDemand。Demand values: LinkDemand. 关联状态：Associated state:

适用于

另请参阅

• PowerModeChangedEventHandler
• SessionEndedEventHandler
• SessionEndingEventHandler
• SessionSwitchEventHandler
• TimerElapsedEventHandler
• UserPreferenceChangedEventHandler
• UserPreferenceChangingEventHandler