This文章说：
如果应用程序必须阻止潜在的系统关闭，它可以调用ShutdownBlockReasonCreate函数。调用者提供将显示给用户的原因字符串。
在ShutdownBlockReasonCreate文档中，它清楚地表明在尝试关闭时，将向用户显示带有原因字符串的对话框窗口：
表示系统无法关闭，并设置在启动系统关闭时向用户显示的原因字符串
并且在this讨论中确认了该对话窗口的外观：
用户可以单击“仍然关闭”。此外，如果用户在几秒钟内未采取任何措施，系统将假定“无论如何都关闭”。
但是，在我调用ShutdownBlockReasonCreate传递当前应用程序的主窗口句柄之后，通过调用ShutdownBlockReasonQuery函数来检索原因字符串来确保函数成功并双重保证它，它不会阻止用户关闭系统而没有对话窗口显示。
为什么它对我的系统没有影响？，我该如何解决这个问题？
我使用管理员（内置）帐户在Windows 10 x64上运行，我使用的代码来自this GitHub存储库：
using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;
using Vanara.PInvoke;
using static Vanara.PInvoke.User32;
namespace Vanara.Windows.Forms.Forms
{
/// <summary>Used to define a set of operations within which any shutdown request will be met with a reason why this application is blocking it.</summary>
/// <remarks>This is to be used in either a 'using' statement or for the life of the application.
/// <para>To use for the life of the form, define a class field:
public class PreventShutdownContext : IDisposable
{
private HandleRef href;
/// <summary>Initializes a new instance of the <see cref="PreventShutdownContext"/> class.</summary>
/// <param name="window">The <see cref="Form"/> or <see cref="Control"/> that contains a valid window handle.</param>
/// <param name="reason">The reason the application must block system shutdown. Because users are typically in a hurry when shutting down the system, they may spend only a few seconds looking at the shutdown reasons that are displayed by the system. Therefore, it is important that your reason strings are short and clear.</param>
public PreventShutdownContext(Control window, string reason)
{
href = new HandleRef(window, window.Handle);
Reason = reason;
}
/// <summary>The reason the application must block system shutdown. Because users are typically in a hurry when shutting down the system, they may spend only a few seconds looking at the shutdown reasons that are displayed by the system. Therefore, it is important that your reason strings are short and clear.</summary>
/// <value>The reason string.</value>
public string Reason
{
get
{
if (!ShutdownBlockReasonQuery(href.Handle, out var reason))
Win32Error.ThrowLastError();
return reason;
}
set
{
if (value == null) value = string.Empty;
if (ShutdownBlockReasonQuery(href.Handle, out var _))
ShutdownBlockReasonDestroy(href.Handle);
if (!ShutdownBlockReasonCreate(href.Handle, value))
Win32Error.ThrowLastError();
}
}
/// <summary>Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.</summary>
public void Dispose()
{
ShutdownBlockReasonDestroy(href.Handle);
}
}
}
...
[DllImport(Lib.User32, SetLastError = true, ExactSpelling = true)]
[return: MarshalAs(UnmanagedType.Bool)]
public static extern bool ShutdownBlockReasonCreate(HWND hWnd, [MarshalAs(UnmanagedType.LPWStr)] string reason);
[DllImport(Lib.User32, SetLastError = true, ExactSpelling = true)]
[return: MarshalAs(UnmanagedType.Bool)]
public static extern bool ShutdownBlockReasonQuery(HWND hWnd, [MarshalAs(UnmanagedType.LPWStr)] StringBuilder pwszBuff, ref uint pcchBuff);
[DllImport(Lib.User32, SetLastError = true, ExactSpelling = true)]
[return: MarshalAs(UnmanagedType.Bool)]
public static extern bool ShutdownBlockReasonDestroy(HWND hWnd);
使用这样的用法：
using (new PreventShutdownContext(this, "This app is super busy right now."))
{
// Do something that can't be interrupted...
}
我按原样尝试了代码，使用了它的P / Invoke定义，还对我使用IntPtr结构的代码进行了一点修改，而不是自定义的HWND结构，并传递给它的主窗口句柄。我在上面的评论中指定的申请。
这是设计的。
documentation（以及您引用的主题）可能会有些误导。
表示系统无法关闭，并设置在启动系统关闭时向用户显示的原因字符串。
如果应用程序必须阻止潜在的系统关闭，它可以调用
ShutdownBlockReasonCreate函数。
此函数实际上只为应用程序设置消息字符串。此功能不会阻止您的应用程序关闭。
要实现关闭块，只需按照您引用的文章中描述的步骤操作即可。您需要对WM_QUERYENDSESSION消息做出反应并返回FALSE（0）。供参考，另请参阅WM_QUERYENDSESSION文档。
您可能还会发现有趣的this topic - 它描述了Windows Vista引入的更改，并包含如何实现关闭逻辑的最佳实践。
顺便说一下，你的应用程序没有特殊的“对话窗口”。将显示标准的Windows关闭UI（根据操作系统版本的不同而不同）。您的应用程序将显示在“阻止关闭的应用程序”列表中，并显示您使用ShutdownBlockReasonCreate函数注册的消息 - 但前提是它返回FALSE消息的WM_QUERYENDSESSION。
如果上述解决方案（WM_QUERYENDSESSION）无法解决问题，则可能是由于忽略此机制的系统设置引起的。
正如@ElektroStudios在他们的研究中发现的那样：
AutoEndTasks注册表值（在HKCU\Control Panel\Desktop注册表项中找到），则关闭不会显示任何UI以允许用户取消关闭。因此在这些情况下创建“取消关闭原因”是没用的，因为在任何情况下都会强制关闭应用程序（以继续关闭）。供参考，请阅读this MS Docs topic。AutoEndTasks注册表值必须为0（零）;否则，任何试图阻止关机的应用程序都将被终止，关机时不会显示任何UI。AutoEndTasks值可以添加到HKEY_USERS\.DEFAULT\Control Panel\Desktop键，该键覆盖HKCU hive和HKU\{SID}中定义的值。这意味着，如果AutoEndTasks在false中是HKCU（0）但在true中是HKU\.DEFAULT（1），那么应用程序将不会阻止系统关闭并且不会显示关闭UI。如果AutoEndTasks在false中是HKU\.DEFAULT但在HKCU中是真的，则应用程序将阻止系统关闭并显示关闭UI。AutoEndTasks值不需要重启/注销系统才能生效。因此，一旦将其设置为正确密钥（例如false）中的HKEY_USERS\.DEFAULT\Control Panel\Desktop，该应用程序将阻止系统关闭，并且当我们完成使用该功能时，我们可以将此值恢复为其先前的状态。如果有人感兴趣，我将在VB.NET中分享我的自定义实现。目前这段代码缺少Windows API定义和我用来读取/写入AutoEndTasks注册表值的方法（下面代码中名称为TweakingUtil.AutoEndTasks的成员），但你可以得到我认为最多的想法关于这一切的重要事情......
Imports Microsoft.Win32
Imports System.Security
''' ----------------------------------------------------------------------------------------------------
''' <summary>
''' Provides a mechanism to prevent any system shutdown/restart/log-off request during the life-cycle of a instance of this class.
''' <para></para>
''' Applications should use this class as they begin an operation that cannot be interrupted, such as burning a CD or DVD.
''' <para></para>
''' This class is to be used in either a <see langword="Using"/> statement or for the life-cycle of the current application.
''' </summary>
''' ----------------------------------------------------------------------------------------------------
''' <remarks>
''' Original source-code: <see href="https://github.com/dahall/Vanara/blob/master/WIndows.Forms/Contexts/PreventShutdownContext.cs"/>
''' </remarks>
''' ----------------------------------------------------------------------------------------------------
''' <example> This is a code example.
''' <code lang="vb">
''' Using psc As New PreventShutdownContext("Critical operation is in progress...")
''' ' Do something that can't be interrupted...
''' End Using
''' </code>
''' </example>
''' ----------------------------------------------------------------------------------------------------
''' <example> This is a code example.
''' <code lang="vb">
''' Public NotInheritable Class Form1 : Inherits Form
'''
''' Private psc As PreventShutdownContext
'''
''' Private Sub AllowShutdown()
''' If (Me.psc IsNot Nothing) Then
''' Me.psc.Dispose()
''' Me.psc = Nothing
''' End If
''' End Sub
'''
''' Private Sub DisallowShutdown()
''' If (Me.psc Is Nothing) Then
''' Me.psc = New PreventShutdownContext("Application defined reason goes here.")
''' End If
''' End Sub
'''
''' Protected Overrides Sub OnShown(ByVal e As EventArgs)
''' Me.DisallowShutdown()
''' MyBase.OnShown(e)
''' End Sub
'''
''' End Class
''' </code>
''' </example>
''' ----------------------------------------------------------------------------------------------------
''' <example> This is a code example using the <see langword="using"/> statement.
''' <code lang="cs">
''' using (new PreventShutdownContext("Critical operation is in progress...")) {
''' // Do something that can't be interrupted...
''' }
''' </code>
''' </example>
''' ----------------------------------------------------------------------------------------------------
''' <code lang="cs">
''' public partial class Form1 : Form {
'''
''' private PreventShutdownContext disallowShutdown;
'''
''' private void AllowShutdown() {
''' if (this.psc != null) {
''' this.psc.Dispose();
''' this.psc = null;
''' }
''' }
'''
''' private void DisallowShutdown() {
''' if (this.psc == null) {
''' this.psc = new PreventShutdownContext("Application defined reason goes here.");
''' }
''' }
'''
''' protected override void OnShown(EventArgs e) {
''' this.DisallowShutdown();
''' base.OnShown(e);
''' }
'''
''' }
''' </code>
''' ----------------------------------------------------------------------------------------------------
Public NotInheritable Class PreventShutdownContext : Implements IDisposable
#Region " Private Fields "
''' <summary>
''' Holds the main window handle for the current application.
''' </summary>
Private ReadOnly hRef As HandleRef
''' <summary>
''' Flag to determine whether the shutdown reason is created.
''' </summary>
Private isReasonCreated As Boolean
''' <summary>
''' Holds the previous value of "HKEY_USERS\.DEFAULT\Control Panel\Desktop" "AutoEndTasks" registry value.
''' <para></para>
''' This registry value is restored when calling <see cref="PreventShutdownContext.Dispose()"/>
''' </summary>
Private ReadOnly previousAutoEndTasksValue As Boolean
#End Region
#Region " Constructors "
''' <summary>
''' Initializes a new instance of the <see cref="PreventShutdownContext"/> class.
''' </summary>
''' <param name="reason">
''' The reason for which the current application must prevent system shutdown.
''' <para></para>
''' Because users are typically in a hurry when shutting down the system,
''' they may spend only a few seconds looking at the shutdown reasons that are displayed by the system.
''' Therefore, it is important that your reason strings are short and clear.
''' </param>
'''
''' <param name="throwOnError">
''' If <see langword="True"/>, an exception will be thrown if
''' the application does not meet the requirements to prevent a system shutdown.
''' <para></para>
''' Default value is <see langword="True"/>.
''' </param>
''' <exception cref="InvalidOperationException">
''' Applications without a user interface can't prevent a system shutdown.
''' </exception>
'''
''' <exception cref="InvalidOperationException">
''' The main window of the current application is not yet created or is not visible.
''' </exception>
'''
''' <exception cref="InvalidOperationException">
''' Only the thread that created the main window of the current application can call this to prevent a system shutdown.
''' </exception>
'''
''' <exception cref="SecurityException">
''' The user does not have the permissions required to create or modify 'AutoEndTasks' registry value.
''' Therefore, the application can't prevent a system shutdown.
''' </exception>
<DebuggerStepThrough>
Public Sub New(ByVal reason As String, Optional ByVal throwOnError As Boolean = True)
If Not Environment.UserInteractive Then
If (throwOnError) Then
Throw New InvalidOperationException(
"Applications without a user interface can't prevent a system shutdown.")
End If
End If
Dim pr As Process = Process.GetCurrentProcess()
Me.hRef = New HandleRef(pr, pr.MainWindowHandle)
If (Me.hRef.Handle = IntPtr.Zero) AndAlso (throwOnError) Then
Throw New InvalidOperationException(
"The main window of the current application is not yet created or is not visible.")
End If
Dim currentThreadId As UInteger = NativeMethods.GetCurrentThreadId()
Dim mainThreadId As Integer = NativeMethods.GetWindowThreadProcessId(Me.hRef.Handle, Nothing)
If (currentThreadId <> mainThreadId) AndAlso (throwOnError) Then
Throw New InvalidOperationException(
"Only the thread that created the main window of the current application can call this to prevent a system shutdown.")
End If
Me.previousAutoEndTasksValue = TweakingUtil.AutoEndTasks
If (Me.previousAutoEndTasksValue) Then
Try
TweakingUtil.AutoEndTasks = False
Catch ex As SecurityException
If (throwOnError) Then
Throw New SecurityException(
"The user does not have the permissions required to create or modify 'AutoEndTasks' registry value. " &
"Therefore, the application can't prevent a system shutdown.", ex)
End If
Catch ex As Exception
If (throwOnError) Then
Throw
End If
End Try
End If
AddHandler SystemEvents.SessionEnding, AddressOf Me.SessionEnding
Me.Reason = reason
End Sub
#End Region
#Region " Properties "
''' <summary>
''' Gets or sets the reason for which the current application must prevent system shutdown.
''' <para></para>
''' Because users are typically in a hurry when shutting down the system,
''' they may spend only a few seconds looking at the shutdown reasons that are displayed by the system.
''' Therefore, it is important that your reason strings are short and clear.
''' </summary>
''' <value>
''' The reason for which the current application must prevent system shutdown.
''' </value>
Public Property Reason As String
Get
Return Me.reason_
End Get
<DebuggerStepThrough>
Set(ByVal value As String)
If value.Equals(Me.reason_, StringComparison.Ordinal) Then
Exit Property
End If
Me.SetReason(value)
Me.reason_ = value
End Set
End Property
''' <summary>
''' ( backing field of <see cref="PreventShutdownContext.Reason"/> property )
''' <para></para>
''' The reason for which the application must prevent system shutdown.
''' </summary>
Private reason_ As String
#End Region
#Region " Event-Handlers "
''' <summary>
''' Handles the <see cref="Microsoft.Win32.SystemEvents.SessionEnding"/> event.
''' </summary>
''' <param name="sender">
''' The source of the event.
''' </param>
'''
''' <param name="e">
''' The <see cref="SessionEndingEventArgs"/> instance containing the event data.
''' </param>
Private Sub SessionEnding(ByVal sender As Object, e As SessionEndingEventArgs)
' By setting "e.Cancel" property to True,
' the application will respond 0 (zero) to "WM_QUERYENDSESSION" message in order to prevent a system shutdown.
'
' For more info:
' https://docs.microsoft.com/en-us/windows/desktop/shutdown/wm-queryendsession
' https://docs.microsoft.com/en-us/windows/desktop/Shutdown/shutdown-changes-for-windows-vista
e.Cancel = True
End Sub
#End Region
#Region " Private Methods "
''' <summary>
''' Sets the reason for which the current application must prevent system shutdown.
''' </summary>
''' <param name="reason">
''' The reason for which the current application must prevent system shutdown.
''' <para></para>
''' Because users are typically in a hurry when shutting down the system,
''' they may spend only a few seconds looking at the shutdown reasons that are displayed by the system.
''' Therefore, it is important that your reason strings are short and clear.
''' </param>
''' <exception cref="Win32Exception">
''' </exception>
<DebuggerStepThrough>
Private Sub SetReason(ByVal reason As String)
Dim succeed As Boolean
Dim win32Err As Integer
If (Me.isReasonCreated) Then
succeed = NativeMethods.ShutdownBlockReasonDestroy(Me.hRef.Handle)
win32Err = Marshal.GetLastWin32Error()
If Not succeed Then
Throw New Win32Exception(win32Err)
End If
End If
succeed = NativeMethods.ShutdownBlockReasonCreate(Me.hRef.Handle, reason)
win32Err = Marshal.GetLastWin32Error()
If Not succeed Then
Throw New Win32Exception(win32Err)
End If
Me.isReasonCreated = True
End Sub
#End Region
#Region " IDisposable Implementation "
''' <summary>
''' Flag to detect redundant calls when disposing.
''' </summary>
Private isDisposed As Boolean
''' <summary>
''' Releases all the resources used by this instance.
''' </summary>
<DebuggerStepThrough>
Public Sub Dispose() Implements IDisposable.Dispose
Me.Dispose(isDisposing:=True)
End Sub
''' <summary>
''' Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
''' Releases unmanaged and, optionally, managed resources.
''' </summary>
''' <param name="isDisposing">
''' <see langword="True"/> to release both managed and unmanaged resources;
''' <see langword="False"/> to release only unmanaged resources.
''' </param>
<DebuggerStepThrough>
Private Sub Dispose(ByVal isDisposing As Boolean)
If (Not Me.isDisposed) AndAlso (isDisposing) Then
RemoveHandler SystemEvents.SessionEnding, AddressOf Me.SessionEnding
NativeMethods.ShutdownBlockReasonDestroy(Me.hRef.Handle)
Me.isReasonCreated = False
Try
TweakingUtil.AutoEndTasks = Me.previousAutoEndTasksValue
Catch
End Try
End If
Me.isDisposed = True
End Sub
#End Region
End Class