Detect Theme Change

As of R1 2022 SP1 RadForm offers the WindowsThemeChanged event which can be used to determine when OS theme change occurs at run-time. Its main purpose is to detect any theme changes on OS level in order to adjust the application theme.

The WindowsSettings.CurrentWindowsTheme can be used to detect the currently active windows theme.

• C#
• VB.NET

private void RadForm_WindowsThemeChanged(object sender, Telerik.WinControls.WindowsThemeChangedEventArgs e)
{
    WindowsTheme newTheme = e.CurrentTheme;
    if (newTheme == WindowsTheme.Light)
    {
        this.BackColor = Color.LightBlue;
    }
    else if (newTheme == WindowsTheme.Dark)
    {
        this.BackColor = Color.DarkBlue;
    }
    else if (newTheme == WindowsTheme.HighContrast)
    {
        this.BackColor = Color.Black;
    }

    this.Text = "Windows Theme is " + newTheme.ToString();
}

Private Sub RadForm_WindowsThemeChanged(sender As Object, e As WindowsThemeChangedEventArgs)
    Dim newTheme As WindowsTheme = e.CurrentTheme

    If newTheme = WindowsTheme.Light Then
        Me.BackColor = Color.LightBlue
    ElseIf newTheme = WindowsTheme.Dark Then
        Me.BackColor = Color.DarkBlue
    ElseIf newTheme = WindowsTheme.HighContrast Then
        Me.BackColor = Color.Black
    End If

    Me.Text = "Windows Theme is " & newTheme.ToString()
End Sub