System.Windows.Forms.Screen 在显示更改后未更新

如何解决System.Windows.Forms.Screen 在显示更改后未更新

正如标题所说，System.Windows.Forms.Screen 在显示更改后没有正确更新其成员。我会具体的：

我有两个显示器，我通过使用 ChangeDisplaySettingsEx 函数以编程方式在它们之间交换主显示器。当我交换监视器时，会引发 SystemEvents.displaySettingsChanged 事件，并且我还可以在 Windows 控制面板中看到更改生效（我的意思是启用或禁用使监视器成为主监视器的复选框），但是，在我的应用程序中，System.Windows.Forms.Screen.PrimaryScreen 对象保持与交换主监视器之前相同。

我从注意到相同的人那里来到 this 线程，并且如 Screen class source-code 中所见，它在拦截 WM_DISPLAYCHANGE 消息时应该更新/更新屏幕对象，所以我尝试了这些电话：

Const HWND_broADCAST As Integer = &HFFFF
Const WM_disPLAYCHANGE As Integer = &H7e

PostMessage(New IntPtr(HWND_broADCAST),WM_disPLAYCHANGE,IntPtr.Zero,IntPtr.Zero)
SendMessage(New IntPtr(HWND_broADCAST),IntPtr.Zero)

但它似乎不起作用，或者我可能没有使用正确的 lParam 和 wParam 调用它，因为 System.Windows.Forms.Screen.PrimaryScreen 对象在将消息发送到所有窗口后保持不变，而 SystemEvents.displaySettingsChanged在这些调用之后引发事件。

在 C# 或 VB.NET 中，我需要在交换它们后、在显示更改后检测真正的主监视器。

因为我在交换监视器时使用 Screen 类而不是使用 Windows API 枚举监视器，所以有什么方法可以解决 Screen 类，也许通过 Reflection 或调度 WM_disPLAYCHANGE，以在显示更改后获取新的/更新的 System.Windows.Forms.Screen.PrimaryScreen 对象？

更新

我还发现了另一个关于此 ...bug? 的证据证明 on MSDN forums。请注意 2012 年的线程并且没有提供解决方案...

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我按照评论中的要求分享了（部分相关的）代码。

''' <summary>
''' Sets the specified <see cref="Screen"/> as primary.
''' <para></para>
''' This functionality will work only with a setup of two monitors. 
''' This functionality does not support three or more monitors.
''' </summary>
''' 
''' <param name="scr">
''' The new primary <see cref="Screen"/>.
''' </param>
<DebuggerStepThrough>
Public Shared Sub SetPrimaryScreen(scr As Screen)

    If (Screen.AllScreens.Count = 1) Then
        Throw New InvalidOperationException("There is only one available monitor.")
    End If

    If (Screen.AllScreens.Count > 2) Then
        Throw New NotSupportedException("Three or more monitor setups are not supported.")
    End If

    If scr.Equals(Screen.PrimaryScreen) Then
        Exit Sub
    End If

    '' DIRTY FIX:
    ' If scr.IsRealPrimaryScreen() Then
    '     Exit Sub
    ' End If

    Dim scrPrimary As Screen = (Screen.AllScreens().Where(Function(s As Screen) s.Primary)).Single()

    '' DIRTY FIX:
    ' Dim scrPrimary As Screen = (Screen.AllScreens().Where(Function(s As Screen) s.IsRealPrimaryScreen())).Single()

    ' Set current primary device position.
    Dim setPositionPrimary As New DevMode(initializeSize:=True) With {.Fields = DeviceModeFields.Position}
    setPositionPrimary.Mode.displayDevMode.Position.X = scr.Bounds.Width
    setPositionPrimary.Mode.displayDevMode.Position.Y = 0
    NativeMethods.ChangedisplaySettingsEx(scrPrimary.DeviceName,setPositionPrimary,ChangedisplaySettingsFlags.UpdateRegistry Or ChangedisplaySettingsFlags.noreset,IntPtr.Zero)

    ' Set secondary device position,and set it as the new primary device.
    Dim setPositionSecondary As New DevMode(initializeSize:=True) With {.Fields = DeviceModeFields.Position}
    setPositionSecondary.Mode.displayDevMode.Position.X = 0
    setPositionSecondary.Mode.displayDevMode.Position.Y = 0
    NativeMethods.ChangedisplaySettingsEx(scr.DeviceName,setPositionSecondary,ChangedisplaySettingsFlags.SetPrimary Or ChangedisplaySettingsFlags.UpdateRegistry Or ChangedisplaySettingsFlags.Reset,IntPtr.Zero)

    ' Update current primary device.
    Dim currentPrimary As New DevMode(initializeSize:=True)
    NativeMethods.ChangedisplaySettingsEx(scrPrimary.DeviceName,currentPrimary,IntPtr.Zero)

    ' Set secondary device as current primary device.
    Dim newPrimary As New DevMode(initializeSize:=True)
    NativeMethods.ChangedisplaySettingsEx(scr.DeviceName,newPrimary,ChangedisplaySettingsFlags.SetPrimary Or ChangedisplaySettingsFlags.UpdateRegistry Or ChangedisplaySettingsFlags.noreset,IntPtr.Zero)

End Sub

交换显示器的使用示例（在两个显示器设置中）：

Dim secondaryMonitor As Screen = (Screen.AllScreens().Where(Function(s As Screen) Not s.Primary)).Single()
SetPrimaryScreen(secondaryScreen)

不能在同一个正在运行的应用程序中调用两次，因为 Screen.PrimaryScreen 在第一次更改后不会更新，因此在后续调用 SetPrimaryScreen 方法时，它会处理错误的/未更新的 { {1}}，我的意思是因为 Screen.PrimaryScreen 始终保持指向同一设备的同一个对象，即使在不再是主要设备之后。

请注意，如果尝试将 Screen.PrimaryScreen 设置为主屏幕（因为它已经应该是主屏幕......但它不是，因为 SetPrimaryScreen 对象没有正确刷新）。

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请注意，我正在寻找一个简单、自然、最佳的解决方案，但我已经设法通过为 Screen.PrimaryScreen 类创建一个名为 {{ 1}}，我将使用它来代替默认的 Screen.PrimaryScreen 属性。

Screen

还有一个 IsRealPrimaryScreen 方法，我将使用它来获取主设备的 Screen.Primary 实例，而不是使用 <HideModuleName> Public Module ScreenExtensions ''' <summary> ''' Determine whether the source <see cref="Screen"/> is the primary device. ''' <para></para> ''' You must always call <see cref="ScreenExtensions.IsRealPrimaryScreen"/> function ''' instead of <see cref="Screen.Primary"/>,''' which does not properly update the class members after a display change: ''' <para></para> ''' <see href="https://stackoverflow.com/questions/67061729/system-windows-forms-screen-is-not-updating-after-a-display-change"/> ''' <para></para> ''' <see href="https://stackoverflow.com/questions/7901247/screen-allscreens-bug-and-posting-a-wm-displaychange-to-a-single-winform-applic"/> ''' </summary> ''' <example> This is a code example. ''' <code language="VB.NET"> ''' Dim primaryMonitor As Screen = (Screen.AllScreens().Where(Function(scr As Screen) scr.IsRealPrimaryScreen)).Single() ''' Dim secondaryMonitor As Screen = (Screen.AllScreens().Where(Function(s As Screen) Not s.IsRealPrimaryScreen)).First() ''' Console.WriteLine(primaryMonitor.DeviceName) ''' Console.WriteLine(secondaryMonitor.DeviceName) ''' </code> ''' </example> ''' <param name="scr"> ''' The source <see cref="Screen"/>. ''' </param> ''' <returns> ''' <see langword="True"/> if the source <see cref="Screen"/> is the primary device; ''' <see langword="False"/> otherwise. ''' </returns> <DebuggerStepThrough> <Extension> <Editorbrowsable(EditorbrowsableState.Always)> Public Function IsRealPrimaryScreen(scr As Screen) As Boolean Dim result As Boolean Dim callback As Delegates.EnumMonitorProc = Function(hMonitor As system.intPtr,hdc As system.intPtr,ByRef rc As NativeRectangle,data As system.intPtr) As Boolean Dim mi As New MonitorInfoEx(initializeSize:=True) NativeMethods.GetMonitorInfo(hMonitor,mi) If (mi.DeviceName.Equals(scr.DeviceName,StringComparison.OrdinalIgnoreCase)) Then result = mi.Flags.HasFlag(MonitorInfoFlags.PrimaryDevice) Return False End If Return True End Function NativeMethods.EnumdisplayMonitors(IntPtr.Zero,callback,IntPtr.Zero) Return result End Function End Module ：

GetRealPrimaryScreen