Assembly: System (in system.dll)
The SystemEvents class provides the ability to respond to specific types of system events.
When a system event is raised, any delegates attached to the event are called using the thread that monitors for system events. Therefore, you should make any calls from your event handlers thread-safe. If you need to call a system event that is not exposed as a member of this class, you can use the InvokeOnEventsThread method.
Do not perform time-consuming processing on the thread that raises a system event handler because it might prevent other applications from functioning.
The HostProtectionAttribute attribute applied to this class has the following Resources property value: MayLeakOnAbort. The HostProtectionAttribute does not affect desktop applications (which are typically started by double-clicking an icon, typing a command, or entering a URL in a browser). For more information, see the HostProtectionAttribute class or SQL Server Programming and Host Protection Attributes.
The following code example registers interest in some system events and then waits for any of those events to occur. The output shown occurs if the user changes the display resolution.
Imports System 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 Not (components Is 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
Windows 98, Windows 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.