ResourceDictionary class

Applies to Windows and Windows Phone

Defines a repository for XAML resources, such as styles, that your app uses. You define the resources in XAML and can then retrieve them in XAML using the StaticResource and ThemeResource markup extensions. You can also access resources with code, but that is less common.

Inheritance

Object
  DependencyObject
    ResourceDictionary

Syntax

Public Class ResourceDictionary
    Inherits DependencyObject
    Implements IDictionary(Of Object, Object), _
    IEnumerable(Of KeyValuePair)

<ResourceDictionary>
  oneOrMoreResources
</ResourceDictionary>


<frameworkElement>
  <frameworkElement.Resources>
    oneOrMoreResources
  </frameworkElement.Resources>
</frameworkElement>

XAML Values

oneOrMoreResources

One or more object elements that support a XAML object element creation syntax and are intended to be referenced as keyed resources. Each resource that you specify must have a unique value as a key.

Attributes

[MarshalingBehavior(Agile)]
[Threading(Both)]
[Version(0x06020000)]
[WebHostHidden()]

Members

The ResourceDictionary class has these types of members:

Constructors

The ResourceDictionary class has these constructors.

ConstructorDescription
ResourceDictionary Initializes a new instance of the ResourceDictionary class.

 

Methods

The ResourceDictionary class has these methods. It also inherits methods from the Object class.

MethodDescription
Add(KeyValuePair) [C#, VB]Adds a new key-value pair to the ResourceDictionary.
Add(Object) [C#, VB]Adds an item to the ResourceDictionary.
Clear Removes all items from this ResourceDictionary.
ClearValue Clears the local value of a dependency property. (Inherited from DependencyObject)
Contains [C#, VB]Returns a value that indicates whether a specified key-value pair exists in the ResourceDictionary.
ContainsKey [C#, VB]Returns a value that indicates whether a specified key exists in the ResourceDictionary.
CopyTo [C#, VB]Copies the elements of the collection to an array, starting at a particular array index.
First [C++]Returns an iterator for the items in the collection.
GetAnimationBaseValue Returns any base value established for a dependency property, which would apply in cases where an animation is not active. (Inherited from DependencyObject)
GetValue Returns the current effective value of a dependency property from a DependencyObject. (Inherited from DependencyObject)
GetView [C++]Retrieves a view against the ResourceDictionary.
HasKey [C++]Returns whether the ResourceDictionary has an entry with the requested key.
Insert [C++]Adds a new entry to the ResourceDictionary.
Lookup [C++]Returns the value from the requested key, if an entry with that key exists.
ReadLocalValue Returns the local value of a dependency property, if a local value is set. (Inherited from DependencyObject)
Remove Removes a specific item from the ResourceDictionary.
Remove(KeyValuePair) [C#, VB]Removes a specific key-value pair from the ResourceDictionary.
SetValue Sets the local value of a dependency property on a DependencyObject. (Inherited from DependencyObject)
TryGetValue [C#, VB]Returns a value that indicates whether a specified key exists in the ResourceDictionary. If an item with that key exists, the item is retrieved as an out parameter.

 

Properties

The ResourceDictionary class has these properties.

PropertyAccess typeDescription

Count [C#, VB]

Read-onlyGets the number of elements contained in the collection.

Dispatcher

Read-onlyGets the CoreDispatcher that this object is associated with. (Inherited from DependencyObject)

IsReadOnly [C#, VB]

Read-onlyGets a value indicating whether the dictionary is read-only.

Item [C#, VB]

Read/writeGets or sets the element value at the specified key index.

Keys [C#, VB]

Read-onlyGets an ICollection object containing the keys of the ResourceDictionary.

MergedDictionaries

Read-onlyGets a collection of the ResourceDictionary dictionaries that constitute the various resource dictionaries in the merged dictionaries.

Size [C++]

Read-onlyGets the number of elements contained in the collection.

Source

Read/writeGets or sets a Uniform Resource Identifier (URI) that provides the source location of a merged resource dictionary.

ThemeDictionaries

Read-onlyGets a collection of merged resource dictionaries that are specifically keyed and composed to address theme scenarios, for example supplying theme values for HighContrast.

Values [C#, VB]

Read-onlyGets an ICollection object containing the values of the ResourceDictionary .

 

Remarks

A resource dictionary is a repository for XAML resources, such as styles, that your app uses. You define the resources in XAML and can then retrieve them in XAML using the StaticResource and ThemeResource markup extensions. You can also access resources with code, but that is less common. You can use resources to enforce that certain values such as brush colors or pixel measurements are used consistently throughout your app. For more info on using resource dictionaries effectively, see ResourceDictionary and XAML resource references.

Uses of ResourceDictionary elements

The ResourceDictionary type is used as the value of two properties, FrameworkElement.Resources and Application.Resources, that are important to the overall structure of a Windows Store app. XAML files that you get from a starting project template for an app will start with initial values for FrameworkElement.Resources, and the app.xaml file might start with initial values for Application.Resources. Exactly what resources are defined there depends on which project starting template you're using.

This XAML shows the use of a FrameworkElement.Resources property. In this case the FrameworkElement is a Page. There is no ResourceDictionary element subordinate to the Page.Resources property element, but its presence is implied; for more info see the "Notes on XAML syntax" section below. The XAML places a Style into the ResourceDictionary with an x:Key value of "TextBlockStyle1". Further down in the XAML, the StaticResource markup extension references the Style in the resource dictionary to provide a value for the Style property of the TextBlock element.

The Style as shown does not actually apply any styling to the TextBlock, but you can add Style properties in Microsoft Visual Studio. You can then use the Style resource as often as you like on the page to enforce uniformity.

You can use Visual Studio to create resource dictionaries. This example was created with these steps: put a TextBlock on the design surface, right click, choose Edit Style / Create Empty, then "This document" to define the new resource in Page.Resources.


<Page
    x:Class="ResourceDictionary_example.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:ResourceDictionary_example"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">
    <Page.Resources>
        <Style x:Key="TextBlockStyle1" TargetType="TextBlock"/>
    </Page.Resources>

    <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
        <TextBlock Style="{StaticResource TextBlockStyle1}" Text="TextBlock"/>
    </Grid>
</Page>


This XAML, from the AppPage.xaml file of the AtomPub sample, shows the use of an Application.Resources property. The XAML places two Style elements into the resource dictionary, making them available throughout the application.


<Application xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    x:Class="AtomPub.App"
    RequestedTheme="Light" >
    <Application.Resources>
        <ResourceDictionary>
            <Style x:Key="TitleStyle" TargetType="TextBlock">
                <Setter Property="Foreground" Value="#707070" />
                <Setter Property="FontFamily" Value="Segoe UI Light" />
                <Setter Property="FontSize" Value="16" />
            </Style>
            <Style x:Key="H1Style" TargetType="TextBlock">
                <Setter Property="Foreground" Value="#212121" />
                <Setter Property="FontFamily" Value="Segoe UI Semilight" />
                <Setter Property="FontSize" Value="26.667" />
                <Setter Property="Margin" Value="0,0,0,25" />
            </Style>
            ...
        </ResourceDictionary>
    </Application.Resources>
</Application> 


This XAML from file MainPage.xaml uses the StaticResource markup extension to access the TitleStyle and H1Style styles:



    ...
    <!-- Header -->
    <StackPanel x:Name="Header" Grid.Row="0">
        <StackPanel Orientation="Horizontal">
            ...
            <TextBlock Text="Windows SDK Samples" VerticalAlignment="Bottom" Style="{StaticResource TitleStyle}" TextWrapping="Wrap"/>
        </StackPanel>
        <TextBlock x:Name="FeatureName" Text="Add Feature Name" Style="{StaticResource H1Style}" TextWrapping="Wrap"/>
    </StackPanel>
     ...


You can factor resources into their own XAML file by using ResourceDictionary as the root element of the file. You can then include those resources in a FrameworkElement.Resources or Application.Resources resource dictionary. To do this you use the ResourceDictionary.MergedDictionaries property or the ResourceDictionary.ThemeDictionaries property of the ResourceDictionary element.

This file, Common/Styles1.xaml, defines Style resources using ResourceDictionary as the root element:


<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

    <Style x:Key="TitleTextStyle" TargetType="TextBlock">
        <Setter Property="FontFamily" Value="Segoe UI Light" />
        <Setter Property="FontSize" Value="16" />
    </Style>
    <Style x:Key="HeaderTextStyle" TargetType="TextBlock">
        <Setter Property="FontFamily" Value="Segoe UI Semilight" />
        <Setter Property="FontSize" Value="26.667" />
        <Setter Property="Margin" Value="0,0,0,25" />
    </Style>
    ...
</ResourceDictionary>

Now suppose there is another file, Common/Styles2.xaml that similarly defines Style resources. This XAML shows how to merge the resources in those two files using the ResourceDictionary.MergedDictionaries property to create an Application.Resources resource dictionary. The XAML also defines two further Style resources and merges them with the resources from the two files.


<Application
    .... >
    <Application.Resources>
        <ResourceDictionary>
            <Style x:Key="ErrorStyle" TargetType="TextBlock">
                <Setter Property="Foreground" Value="DarkRed"/>
                <Setter Property="FontFamily" Value="Segoe UI Semilight" />
                <Setter Property="FontSize" Value="15" />
            </Style>
            <Style x:Key="StatusStyle" TargetType="TextBlock">
                <Setter Property="Foreground" Value="Black"/>
                <Setter Property="FontFamily" Value="Segoe UI Semilight" />
                <Setter Property="FontSize" Value="15" />
            </Style>
            <ResourceDictionary.MergedDictionaries>
                <!-- 
                    Styles that define common aspects of the platform look and feel
                 -->
                <ResourceDictionary Source="Common/Styles1.xaml"/>
                <ResourceDictionary Source="Common/Styles2.xaml"/>
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </Application.Resources>
</Application>

For info on how merged dictionary resources are resolved, see the "Merged resource dictionaries" section of ResourceDictionary and XAML resource references.

The x:Key property

In XAML, the keys for ResourceDictionary items are declared by setting the x:Key attribute on elements that represent the XAML resources. Typically, if you try to put a child element that does not have a key value into a ResourceDictionary, this throws a XAML parse exception or a Windows Runtime exception. The exception condition might also be noted as a warning by XAML design surfaces. However, there are three notable cases where a ResourceDictionary child element won't require an x:Key value:

  • A Style resource can use its TargetType value as the implicit resource key. For more info on how implicit keys for styles and control templates work, see Quickstart: Styling controls.
  • The ResourceDictionary elements with Source values that represent ResourceDictionary.MergedDictionaries values can't have an x:Key attribute on ResourceDictionary. Within each merged dictionary file, (the one referenced by URI as its Source) you do need keys for each resource.
  • The x:Name attribute can be used instead of x:Key attribute, for legacy reasons. However, x:Name by itself doesn't enable XAML resource lookup of that item. The x:Name attribute identifying convention is used for certain scenarios such as defining storyboarded animations. For more info, see x:Name attribute.

Iterating through a ResourceDictionary

You can iterate through a ResourceDictionary in C# or Microsoft Visual Basic. In many cases, such as using foreach syntax, the compiler does this casting for you and you won't need to cast to IEnumerable explicitly. If you do need to cast explicitly, for example if you want to call GetEnumerator, cast to IEnumerable<T> with a KeyValuePair<Object,Object> constraint.

ResourceDictionary and Visual Studio

Visual Studio provides an Add New Item page choice for a resource dictionary. Use this option whenever you want to define a new loose XAML resource dictionary, for example to serve as the source for a merged dictionary. Visual Studio also adds a loose XAML resource dictionary to the project whenever you use Add New Item to create a templated control. This resource dictionary provides the default theme templates. Visual Studio might create a new ResourceDictionary for you in your XAML if you are editing copies of styles or templates and a ResourceDictionary for your chosen resource location (app, page, or standalone) doesn't exist yet.

Notes on XAML syntax

Notice that the XAML implicit collection syntax for ResourceDictionary does not include an object element for the ResourceDictionary. This is an example of XAML implicit collection syntax; a tag representing the collection element can be omitted. The elements that are added as items to the collection are specified as child elements of a property element of a property whose underlying type supports a dictionary / map Add method.

For a merged resource dictionary, you do need to explicitly declare a ResourceDictionary object element, so that you can also declare the ResourceDictionary.MergedDictionaries property element and Source. Thus there are a minimum of two ResourceDictionary object elements involved, and you use this syntax.


<ResourceDictionary>
  <ResourceDictionary.MergedDictionaries>
    <ResourceDictionary Source="uri" />
    ...
  </ResourceDictionary.MergedDictionaries>
...
</ResourceDictionary>

In this syntax the outer ResourceDictionary is the primary ResourceDictionary. The inner ResourceDictionary is the ResourceDictionary being merged.

For the implicit collection usage, the placeholder as appropriate for the property FrameworkElement.Resources is shown. You could also use this implicit collection usage for the Application.Resources property, or potentially for a custom property that uses ResourceDictionary as its property type.

Shareable types and UIElement types

A resource dictionary is a technique for defining shareable types and values of these types in XAML. Not all types or values are suitable for usage from a ResourceDictionary. Examples of types where sharing is supported include Style, any FrameworkTemplate subclass, the XAML intrinsic data types, brushes, colors, and transforms. For more info on which types are considered shareable, see ResourceDictionary and XAML resource references. Generally, UIElement-derived types are not shareable unless they come from templates and application of a template on a specific control instance. Excluding the template case, a UIElement is expected to exist in only one place in an object tree after it is instantiated, and having a UIElement be shareable would potentially violate this principle.

In practice, the vast majority of the resources defined in a ResourceDictionary will be one of these:

  • Control templates for a control, including its visual states.
  • Supporting styles for parts of controls
  • Styles for elements that are part of typical app UI but aren't controls, like TextBlock
  • Data templates for controls and panels that use data binding
  • Specific Brush values, mostly SolidColorBrush
  • Strings or other constants that never need to be localized (strings and constants that do need to be localized shouldn't be in a ResourceDictionary; for more info see Quickstart: Translating UI resources)

Accessing a ResourceDictionary object in code

The API that your code uses to access the resources in a ResourceDictionary depends on which programming language you use:

For more info on how to use ResourceDictionary in code, see "Using a ResourceDictionary from code" section of ResourceDictionary and XAML resource references.

System resources

Some theme resources reference system resource values as an underlying sub-value. A system resource is a special resource value that isn't found in any XAML resource dictionary. These values rely on behavior in Windows Runtime XAML support to forward values from the system itself, and represent them in a form that a XAML resource can reference.

Resource loading optimization in Windows 8.1

Starting with Windows 8.1, there's a resource loading optimization that's enabled by the app model and the Windows Runtime XAML parser. For Windows 8, the XAML parser loaded resources from app.xaml and created each of them as objects as part of startup. That wasn't very efficient if there were big dictionaries there. Also, those resources included the items that were needed by all three themes, and two of the three themes wouldn't even be active. Starting with Windows 8.1, the XAML parser only creates the resources when they're specifically requested. The request might come from other resources or from app or page XAML as each is loaded. This parser behavior minimizes the time it takes to read the app-level dictionary at startup time, and enables the first app page to load faster in most cases. Resources needed by other currently inactive themes are only loaded if that theme is chosen to become the active theme by the user. At that time, any resource where the ThemeResource markup extension was used for the request is recalculated based on the newly active theme.

Windows 8 behavior

Windows 8 didn't have the optimizations described above. The ResourceDictionary for Application.Resources had to finish parsing before any page other than the splash screen could load into the app's Window. Because of this you might see some differences in timing when you retarget your app for Windows 8.1. The app should be loading faster, however it may not be possible to isolate this improvement versus other changes you've made to your app code as part of retargeting. Some of the places where you might see evidence of timing changes due to optimized resource loading include when the constructors are called by the parser, for objects like Application objects, converters, or other custom classes. Apps that were compiled for Windows 8 but running on Windows 8.1 continue to use the Windows 8 behavior.

For more info on performance and XAML resource factoring, see Optimize loading XAML.

Requirements

Minimum supported client

Windows 8 [Windows Store apps only]

Minimum supported server

Windows Server 2012 [Windows Store apps only]

Minimum supported phone

Windows Phone 8.1 [Windows Runtime apps only]

Namespace

Windows.UI.Xaml
Windows::UI::Xaml [C++]

Metadata

Windows.winmd

See also

DependencyObject
IMap(Object, Object)
IDictionary<TKey,TValue>
ResourceDictionary and XAML resource references
Application resources and localization sample
ThemeResource markup extension
StaticResource markup extension
x:Key attribute

 

 

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