How to set default WPF Window Style in app.xaml?

Question

I am trying to set the default Style for every window in my WPF Windows application in my app.xaml. So far i have this in app.xaml:

<Application.Resources>
    <ResourceDictionary>
        <Style x:Key="WindowStyle" TargetType="{x:Type Window}">
            <Setter Property="Background" Value="Blue" />
        </Style>
    </ResourceDictionary>
</Application.Resources>

I can get the window to appear with this style when running the app (but not is VS designer) by specifically telling the window to use this style via:

Style="{DynamicResource WindowStyle}

This works, but is not ideal. So how do I:

1. Have all windows automatically use the style (so i don't have to specify it on every window)?
2. Have VS designer show the style?

Thanks!

Answer 1

I investigated this one for some days now and made it work through the Constructor of my custom Window Class:

public class KWindow : Window
{
        public KWindow()
        {
            this.SetResourceReference(StyleProperty, typeof(KWindow));
        }

        static KWindow()
        {
            DefaultStyleKeyProperty.OverrideMetadata(typeof(KWindow), new FrameworkPropertyMetadata(typeof(KWindow)));

        }

        public override void OnApplyTemplate()
        {
            base.OnApplyTemplate();

            // gets called finally
        }
}

Hope it helps someone

Answer 2

The designer is not working because you're specifying a DynamicResource. Please change this to StaticResource and all will be well.

To apply to all windows, you should remove the x:Key from the style. Setting the TargetType implicitly sets the x:Key to whatever is in TargetType. However, in my tests, this is not working, so I am looking into it.

If I set the TargetType to x:Type TextBlock, the designer works perfectly, it just seems to be the Window that is showing different behaviour.

Answer 3

1. you will save all the styles in one xaml file(example design.xaml)

2. and then call that (design.xaml) xaml file in all the pages like this way

Like:

<ResourceDictionary.MergedDictionaries>
                <ResourceDictionary  Source="Design.xaml"/>                
</ResourceDictionary.MergedDictionaries>

Answer 4

For those this struggling with a solution to the problem: How can I have a custom style be automtically applied to all my Window derived types? Below is the solution I came up with

NOTE: I really didn't want to derive from the Window type or have to insert XAML on each window to force a style update etc. for reasons specific to my project (consumers of my product us my generic reusable style library and create their own layout/windows etc.) so I was really motivated to figure a solution out that worked that I was willing to live with any side effects

Need to iterate through all the instantiated windows and simply force them to use the new custom style you have defined for the Window type. This works great for windows that are already up but when a window or child window is instantiated it won't know to use the new/custom type that has been declared for its base type; the vanilla Window type. So the best I could come up with was to use the LostKeyBoardFocus on the MainWindow for when it loses Focus to a ChildWindow (IOW When a child window has been created) and then invoke this FixupWindowDerivedTypes().

If someone has a better solution for "detecting" when any kind of window derived type is instantiated and thus call the FixupWindowDerivedTypes() that would be great. There may be something useful with handling the WM_WINDOWPOSCHANGING in this area as well.

So this solution is not elegant per say but gets the job done without me having to touch any code or XAML related to my windows.

   public static void FixupWindowDerivedTypes()
    {
        foreach (Window window in Application.Current.Windows)
        {
           //May look strange but kindly inform each of your window derived types to actually use the default style for the window type

                    window.SetResourceReference(FrameworkElement.StyleProperty, DefaultStyleKeyRetriever.GetDefaultStyleKey(window));
                }
            }
        }
    }


//Great little post here from Jafa to retrieve a protected property like DefaultStyleKey without using reflection.
http://themechanicalbride.blogspot.com/2008/11/protected-dependency-properties-are-not.html

//Helper class to retrieve a protected property so we can set it
internal class DefaultStyleKeyRetriever : Control
{
    /// <summary>
    /// This method retrieves the default style key of a control.
    /// </summary>
    /// <param name="control">The control to retrieve the default style key 
    /// from.</param>
    /// <returns>The default style key of the control.</returns>
    public static object GetDefaultStyleKey(Control control)
    {
        return control.GetValue(Control.DefaultStyleKeyProperty);
    }
}

Answer 5

To add on to what Ray says:

For the Styles, you either need to supply a Key/ID or specify a TargetType.

If a FrameworkElement does not have an explicitly specified Style, it will always look for a Style resource, using its own type as the key
- Programming WPF (Sells, Griffith)

If you supply a TargetType, all instances of that type will have the style applied. However derived types will not... it seems. <Style TargetType="{x:Type Window}"> will not work for all your custom derivations/windows. <Style TargetType="{x:Type local:MyWindow}"> will apply to only MyWindow. So the options are

• Use a Keyed Style that you specify as the Style property of every window you want to apply the style. The designer will show the styled window.

.

    <Application.Resources>
        <Style x:Key="MyWindowStyle">
            <Setter Property="Control.Background" Value="PaleGreen"/>
            <Setter Property="Window.Title" Value="Styled Window"/>
        </Style>
    </Application.Resources> ...
    <Window x:Class="MyNS.MyWindow" Style="{StaticResource MyWindowStyleKey}">  ...

• Or you could derive from a custom BaseWindow class (which has its own quirks), where you set the Style property during the Ctor/Initialization/Load stage once. All Derivations would then automatically have the style applied. But the designer won't take notice of your style You need to run your app to see the style being applied.. I'm guessing the designer just runs InitializeComponent (which is auto/designer generated code) so XAML is applied but not custom code-behind.

So I'd say explicitly specified styles are the least work. You can anyways change aspects of the Style centrally.

Answer 6

Considering Gishu's answer I figured out one more workaround. But it could be little bit weird. If you use MVVM pattern you could remove code-behind of your window and x:Class markup in XAML file. So you will get an instance of window or your custom window but not a some instance of 'MainWindow' class that is derived from 'Window' class and marked as partial. I'm making VS-like window so I had to inherit window class and extend it functionality. In that case it will be possible to make new window class as partial that would allow us to make code-behind without inheritance.