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...
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）。
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
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