Using Styles in XAML

Question

I have defined styles in Styles.xaml within a ResourceDictionary, then I "import" them at the root element in my main window

        <RelativePanel.Resources>
            <Style TargetType="Button" x:Key="Default">
                <Setter Property = "Margin" Value="10"/>
            </Style>
            <ResourceDictionary x:Key="aaa">
                <ResourceDictionary.MergedDictionaries>
                    <ResourceDictionary Source="Styles.xaml"/>
                </ResourceDictionary.MergedDictionaries>
            </ResourceDictionary>
        </RelativePanel.Resources>

My first question is why did the compiler forced me to define a key for the ResourceDictionary, I had another mini project to test this method of importing styles and had no errors

        <Grid.Resources>
            <ResourceDictionary>
                <ResourceDictionary.MergedDictionaries>
                    <ResourceDictionary Source="Styles.xaml"/>
                </ResourceDictionary.MergedDictionaries>
            </ResourceDictionary>
        </Grid.Resources>

Second question would be, how should I use this key when calling for the style at Style="{StaticResource ...}"

Answer 1

Hello,

Welcome to Microsoft Q&A!

The first thing needs to know is that when you use the Resource property of the framework element, the element implicitly creates a resource dictionary for you. Like this:

 <StackPanel.Resources>
     <x:String x:Key="greeting">Hello world</x:String>
 </StackPanel.Resources>

But when you want to add merged dictionaries with other styles, you will need to do it a little bit different. You could declare <ResourceDictionary> first, then add things to its <ResourceDictionary.MergedDictionaries> collection. After <ResourceDictionary.MergedDictionaries>…</ResourceDictionary.MergedDictionaries>, you can optionally put additional resources in your main dictionary.

So, the code should be like this for your first question, you don't need to add a key for the ResourceDictionary. And you won't worry for the second question, just call the styles as usual.

   <RelativePanel.Resources>

       <!--This works-->
       <ResourceDictionary >
           <ResourceDictionary.MergedDictionaries>
               <ResourceDictionary Source="Styles.xaml"/>
           </ResourceDictionary.MergedDictionaries>
           <Style TargetType="Button" x:Key="Default">
               <Setter Property = "Margin" Value="10"/>
           </Style>
       </ResourceDictionary>

   </RelativePanel.Resources>

For more details about ResourceDictionary, please refer to this document: ResourceDictionary and XAML resource references

Thank you.

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