How do I darken all screen area and glow my opened window in WPF?

Question

In WPF, how do I darken all screen area when opening a new window?

Also after the window is closed, how do I revert the temporary effect?

Answer 1

Here is my version, if you want gray out and blur the parent window:

private void btnOpenSettings_Click(object sender, RoutedEventArgs e)
    {
        // settings for the parent window
        // set the transparency to the half
        this.Opacity = 0.5;
        // blur the whole window
        this.Effect = new BlurEffect();

        // Set the options for the settings (child) window
        SettingsForm wdwSettings = new SettingsForm() 
        { 
            Owner = this,
            ShowInTaskbar = false,
            Topmost = true
        };

        // Open the child window
        wdwSettings.ShowDialog();

        //restore Opacity and remove blur after closing the child window
        this.Opacity = 1;
        this.Effect = null;
    }