WPF: Detect Screen Resolution Change (without constantly polling SystemParameters)?

[Jules Winfield]

Hello Friend,

I need to take a particular non-UI-related action when the user changes the
screen resolution. How can I detect when the screen resolution is changed by
the user?

Here's my first approach. I created an internal class called ScreenSize that
exposes a dependency property called ScreenWidth:

internal class ScreenSizeependencyObject{

public DependencyProperty
ScreenWidthProperty=DependencyProperty.Register("ScreenWidth",typeof(double),typeof(ScreenSize),new
PropertyMetadata(new PropertyChangedCallback(OnScreenWidthChanged)));

public double ScreenWidth{
get{return (double)this.GetValue(ScreenWidthProperty);}
set{this.SetValue(ScreenWidthProperty,value);}
}

private static void OnScreenWidthChanged(DependencyObject
d,DependencyPropertyChangedEventArgs e){
Debug.Print("Changed");
}

}

...and then I defined an instance of this class in the resources section of
the XAML file for my application:

<ResourceDictionary>
<aiacreenSize x:Key="ScreenSize" ScreenWidth="{DynamicResource {xtatic
SystemParameters.PrimaryScreenWidthKey}}"/>
</ResourceDictionary>

My expectation was that OnScreenWidthChanged() would be called whenever the
user manually changes the resolution. The reality, however, is that
OnScreenWidthChanged() is called once at startup and then never again --
even if the screen resolution is manually changed. Do you have an alternate
approach?

Thanks,


Jules

 

[Linda Liu]

Hi Jules,

Based on my understanding,you'd like to get notified in your WPF application
when the user changes the screen resolution. If I'm off base, please feel
free to let me know.

In your scenario, you use an instance of the ScreenSize class in the
resource dictionary within a window and bind the
SystemParameters.PrimaryScreenWidthKey to the instance's ScreenWidth
dependency property. When the application starts up, this ScreenWidth
property is assigned. However, the ScreenSize instance used in the resource
section doesn't have a resource tree, so when the system parameter changes,
the ScreenWidth property won't be updated immediately.

If what you really want is only to get notified in the application when the
screen resolution is changed, I suggest that you subscribe and handle the
DisplaySettingsChanged event of SystemEvents in the window.

For example:

public partial class Window1 : Window
{
public Window1()
{
InitializeComponent();
SystemEvents.DisplaySettingsChanged += new
EventHandler(SystemEvents_DisplaySettingsChanged);
}

void SystemEvents_DisplaySettingsChanged(object sender, EventArgs e)
{
Debug.WriteLine("display settings changed");
}
}

Hope this hleps.
If you have any question, please feel free to let me know.

Sincerely,
Linda Liu
Microsoft Online Community Support

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[Jules Winfield]

If what you really want is only to get notified in the application when

the screen resolution is changed, I suggest that you subscribe and handle
the DisplaySettingsChanged event of SystemEvents in the window.

Thanks. That's exactly the answer I needed.