var darkmode =  new Darkmode();
darkmode.toggle();

''' <summary>
''' Handles the <see cref="ChromiumWebBrowser.IsBrowserInitializedChanged"/> event 
''' for all of the <see cref="ChromiumWebBrowser1"/> control.
''' </summary>
''' 
''' <param name="sender">
''' The source of the event.
''' </param>
''' 
''' <param name="e">
''' The <see cref="EventArgs"/> instance containing the event data.
''' </param>
<DebuggerStepperBoundary>
Private Sub ChromiumWebBrowser1_IsBrowserInitializedChanged(sender As Object, e As EventArgs) _
    Handles ChromiumWebBrowser1.IsBrowserInitializedChanged
 
    Dim browser As ChromiumWebBrowser = DirectCast(sender, ChromiumWebBrowser)
    If browser.IsBrowserInitialized Then
        browser.GetDevToolsClient().Emulation.SetAutoDarkModeOverrideAsync(True)
    End If
 
End Sub

''' <summary>
''' Handles the <see cref="ChromiumWebBrowser.FrameLoadEnd"/> event 
''' for all of the <see cref="ChromiumWebBrowser1"/> control.
''' </summary>
''' 
''' <param name="sender">
''' The source of the event.
''' </param>
''' 
''' <param name="e">
''' The <see cref="FrameLoadEndEventArgs"/> instance containing the event data.
''' </param>
<DebuggerStepperBoundary>
Private Sub ChromiumWebBrowser1_FrameLoadEnd(sender As Object, e As FrameLoadEndEventArgs) _
    Handles ChromiumWebBrowser1.FrameLoadEnd
 
    If e.Frame.IsMain Then
        Dim browser As ChromiumWebBrowser = DirectCast(sender, ChromiumWebBrowser)
        browser.GetDevToolsClient().Emulation.SetAutoDarkModeOverrideAsync(True)
    End If
 
End Sub

''' <summary>
''' Ennable or disable dark mode for the source <see cref="ChromiumWebBrowser"/> object.
''' </summary>
''' 
''' <param name="browser">
''' The source <see cref="ChromiumWebBrowser"/> which to ennable or disable dark mode.
''' </param>
''' 
''' <param name="enableDarkMode">
''' <see langword="True"/> to enable dark mode, <see langword="False"/> otherwise.
''' </param>
''' 
''' <returns>
''' Returns a <see cref="DevToolsMethodResponse"/> object containing information about success or error.
''' </returns>
''' 
''' <exception cref="InvalidOperationException">
''' Browser has not been initialized.
''' </exception>
<Extension>
<DebuggerStepThrough>
Public Async Function SetDarkModeAsync(browser As ChromiumWebBrowser, enableDarkMode As Boolean) As _
    Task(Of DevToolsMethodResponse)
 
    If browser Is Nothing Then
        Throw New ArgumentNullException(paramName:=NameOf(browser))
    End If
 
    If Not browser.IsBrowserInitialized Then
        Throw New InvalidOperationException("Browser has not been initialized.")
    End If
 
    Return Await browser.GetDevToolsClient().Emulation.SetAutoDarkModeOverrideAsync(enableDarkMode)
 
End Function