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 in 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:

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

Thanks!

score 49 · Answer 1 · answered Jan 20 '09 at 10:34

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.

You can 'cascade' style by using the BasedOn property. `BasedOn="{StaticResource {x:Type Window}}"` However, I haven't been able to get Window to accept the un-keyed styles. I guess it's because they don't recognize the derived types, as you said. — Benny Jobigan, Feb 04 '10 at 12:16
Your code is full of bugs and doesnt even come close to compiling and is effectively useless, for instance using `MyWindowStyleKey` and `MyWindowStyle`. One of the many reasons why nearly 9 years later it has not been accepted. — Matt, Feb 10 '18 at 01:37

score 24 · Answer 2 · edited May 23 '17 at 11:46

Know this is years later, but since the question is still up here...

Create a resource dictionary in your project (Right-click the project...)

I'll create a new folder under the Project called "Assets" and put "resourceDict.XAML in it.

Add the code to resourceDict.XAML:

<Style x:Key="WindowStyle" Target Type="Window" >
     <Setter Property="Background" Value="Blue" />
</Style>

In your Project XAML file add the following under Window:
```
<Window.Resources>
    <ResourceDictionary>
        
        <Style TargetType="{x:Type Rectangle}" />
        <ResourceDictionary.MergedDictionaries>
            <ResourceDictionary Source="/Assets/resourceDict.XAML" />
        </ResourceDictionary.MergedDictionaries>
    <ResourceDictionary>
</Window.Resources>
```
ref the following web site: Trouble referencing a Resource Dictionary that contains a Merged Dictionary "There is a bug: if all your default styles are nested in merged dictionaries three levels deep (or deeper) the top dictionary does not get flagged so the search skips it. The work around is to put a default Style to something, anything, in the root Dictionary." And it seems to fix things reliably. Go figure...
And finally, under Window, maybe after Title, but before the final Window '>' :
```
Style="{DynamicResource windowStyle}"
```
And you'll need to add the code in steps 3 & 4 to every project to which you want the style to apply.

If you wanted to use a gradient background rather than a solid color, add the following code to the resourceDict.XAML:

<LinearGradientBrush x:Key="windowGradientBackground" StartPoint="0,0"
        EndPoint="0,1" >
<GradientStop Color= "AliceBlue" Offset="0" />
<GradientStop Color= "Blue" Offset=".75" />
</LinearGradientBrush>

And modify your Style Setter for the background color to read:

<Setter Property="Background" Value="{DynamicResource
        windowGradientBackground}" />

Steps 3 & 4 need to be repeated in each project.XAML file as described above, but hey, you get uniform Windows across the Solution! And the same process could apply to any controls you want to have a uniform look as well, buttons, whatever.

For anyone coming into this late, hope this helps as I'm sure the original posters got this all figured out years ago.

Paul

The tip here about not embedding MergedDictionaries within MergedDictionaries was the solution for me. Simply declare all theme files directly from the App.xaml So thanks! — jv_, Sep 21 '17 at 15:16
Edit please. In resources file property name is `TargetType` , not `Target Type`. — aquaprogit, Jan 05 '19 at 14:40
I'm not sure what Paul means by "project.xaml". The app.xaml? The window.xaml? If it's the latter then how does this help? We still have to apply the style manually to each window we create. The goal is to create a general global style for a window without having to explicitly apply it to each instance. It could be that I'm not getting it, and if so, I would like someone to please enlighten me. I'd love to get this working. — Mike, Aug 28 '21 at 04:06

score 8 · Answer 3 · answered Jan 10 '09 at 23:23

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.

Yea, I just ran into that same problem. Gishu said above that it seems the implicit style for Window won't apply to your window, since it's really a derived class. — Benny Jobigan, Feb 04 '10 at 12:19

score 7 · Answer 4 · answered Jan 31 '17 at 15:15

7

You can add this code to your App.xaml.cs file:

        FrameworkElement.StyleProperty.OverrideMetadata(typeof(Window), new FrameworkPropertyMetadata
        {
            DefaultValue = Application.Current.FindResource(typeof(Window))
        });

After this, the style applied to the Window type will also apply to all types derived from Window

answered Jan 31 '17 at 15:15

STiLeTT

1,023
10
23

1

This is the only solution that works for my `BaseWindow` class. Thank you! – pinki May 24 '17 at 08:33

score 4 · Answer 5 · answered Feb 25 '15 at 09:58

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

This works brilliantly. I am finally able to specify TargetType in my style and have all my derived windows apply it at runtime.. So, this is a solution that works for both XAML designer and during runtime. — Oyvind, Jan 14 '19 at 11:48

score 1 · Answer 6 · answered May 10 '13 at 17:06

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);
    }
}

Crossman · Answer 7 · 2014-02-02T10:43:47.203

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.

score -2 · Answer 8 · edited Nov 18 '13 at 09:50

-2

you will save all the styles in one xaml file(example design.xaml)
and then call that (design.xaml) xaml file in all the pages like this way

Like:

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

edited Nov 18 '13 at 09:50

kleopatra

51,061
28
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answered Nov 18 '13 at 09:25

Alex Anbu

1

1

OP's goal is to NOT have to set the style every time. – Oyvind Jan 14 '19 at 11:26

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

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