如何将 ResourceDictionary 样式应用于代码隐藏文件中的控件

Question

I have a ResourceDictionary as defined below in its own file:

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:local="clr-namespace:WordSearch">

<Style x:Key="labelStyle">
        <Setter Property="Label.Foreground" Value="#8860D0"/>
    </Style>

</ResourceDictionary>

In my code behind file I have a list of labels containing some Label controls.

private List<Label> labels;

Is there any way I can apply the style from the ResourceDisctionary to all my labels? So far I got as far as this but the style isn't applied:

ResourceDictionary skin = Application.LoadComponent(new Uri("BrightTheme.xaml", UriKind.Relative)) as ResourceDictionary;
            Resources.MergedDictionaries.Add(skin);

            for (int i = 0; i < labels.Count; i++)
            {
                labels[i].Style = (Style)skin["labelStyle"];
            }

Answer 1

As I stated in my comment before answering, if the ultimate goal is theming, then it doesn't matter if your labels are generated automatically by the program or hardcoded in xaml. The approach you want to take is to swap your ResourceDictionary theme, which it looks like you are trying to do, although I see you are only adding not removing.

Also, you don't need to set each Label's Style to a Key. Because it is up to the ResourceDictionary to apply the Label's overall Style.

Here's an example:

Dictionary1.xaml: This is one theme. Notice the 2nd Style is the one that applies labelStyle to ALL of the labels

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <Style x:Key="labelStyle" TargetType="Label">
        <Setter Property="Foreground" Value="#8860D0"/>
    </Style>
    <Style TargetType="{x:Type Label}" BasedOn="{StaticResource labelStyle}"/>
</ResourceDictionary>

Dictionary2.xaml: This is another theme

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:local="clr-namespace:ApplyLabelStyleOnUserControl">
    <Style x:Key="labelStyle" TargetType="Label">
        <Setter Property="Foreground" Value="DarkGreen"/>
    </Style>
    <Style TargetType="{x:Type Label}" BasedOn="{StaticResource labelStyle}"/>
</ResourceDictionary>

MainWindow.xaml

    <Grid>
        <StackPanel>
            <Button Content="Swap Theme" Click="Button_Click" Margin="15"/>
            <local:UserControl1 x:Name="userControl1" Margin="5"/>
        </StackPanel>
    </Grid

MainWindow.xaml.cs

        private bool useSecondTheme;

        public MainWindow()
        {
            InitializeComponent();
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            useSecondTheme = !useSecondTheme;
            userControl1.SwapTheme(useSecondTheme);
        }

UserControl1.xaml

    <Grid>
        <StackPanel>
            <ListBox ItemsSource="{Binding MyLabels}">
                <ListBox.ItemContainerStyle>
                    <Style TargetType="ListBoxItem">
                        <Setter Property="Template">
                            <Setter.Value>
                                <ControlTemplate TargetType="ListBoxItem">
                                    <Border>
                                        <Label Margin="5" Content="{Binding}"/>
                                    </Border>
                                </ControlTemplate>
                            </Setter.Value>
                        </Setter>
                    </Style>
                </ListBox.ItemContainerStyle>
            </ListBox>
            <Button Click="Button_Click" Content="Add Random Label" Margin="5"/>
        </StackPanel>
    </Grid>

UserControl1.xaml.cs: Look specifically at SwapTheme

using System;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;
using System.Windows;
using System.Windows.Controls;

namespace ApplyLabelStyleOnUserControl
{
    /// <summary>
    /// Interaction logic for UserControl1.xaml
    /// </summary>
    public partial class UserControl1 : UserControl, INotifyPropertyChanged
    {
        private ObservableCollection<string> myLabels;

        public ObservableCollection<string> MyLabels
        {
            get
            {
                if (this.myLabels == null)
                    this.myLabels = new ObservableCollection<string>();
                return this.myLabels;
            }
        }
        private static Random random = new Random();
        public string RandomString(int length)
        {
            const string chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
            return new string(Enumerable.Repeat(chars, length)
              .Select(s => s[random.Next(s.Length)]).ToArray());
        }

        public UserControl1()
        {
            InitializeComponent();
            this.DataContext = this;
            this.Loaded += OnLoaded;
        }

        private void OnLoaded(object sender, RoutedEventArgs e)
        {
            // Initialize it with 5 random strings, but allow more labels to be added with a button on the UI.
            MyLabels.Add(RandomString(25));
            MyLabels.Add(RandomString(25));
            MyLabels.Add(RandomString(25));
            MyLabels.Add(RandomString(25));
            MyLabels.Add(RandomString(25));
        }

        public event PropertyChangedEventHandler PropertyChanged;

        /// <summary>
        /// Swaps between two themes
        /// </summary>
        /// <param name="useSecondTheme">when true it uses Dictionary2.xaml resource dictionary, otherwise it uses Dictionary1.xaml</param>
        internal void SwapTheme(bool useSecondTheme)
        {
            if (useSecondTheme)
            {
                // Remove the old theme
                ResourceDictionary oldSkin = Application.LoadComponent(new Uri("Dictionary1.xaml", UriKind.Relative)) as ResourceDictionary;
                Resources.MergedDictionaries.Remove(oldSkin);

                // Add the new theme
                ResourceDictionary newSkin = Application.LoadComponent(new Uri("Dictionary2.xaml", UriKind.Relative)) as ResourceDictionary;
                Resources.MergedDictionaries.Add(newSkin);
            }
            else
            {
                // Remove the old theme
                ResourceDictionary oldSkin = Application.LoadComponent(new Uri("Dictionary2.xaml", UriKind.Relative)) as ResourceDictionary;
                Resources.MergedDictionaries.Remove(oldSkin);

                // Add the new theme
                ResourceDictionary newSkin = Application.LoadComponent(new Uri("Dictionary1.xaml", UriKind.Relative)) as ResourceDictionary;
                Resources.MergedDictionaries.Add(newSkin);
            }
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            MyLabels.Add(RandomString(25));
        }
    }
}

Whenever I click the "Swap Theme" button, it will toggle between the two ResourceDictionaries that I defined:

Answer 2

Try to create an actual ResourceDictionary and set its Source instead of calling Application.LoadComponent :

ResourceDictionary skin = new ResourceDictionary() 
{ 
    Source = new Uri("BrightTheme.xaml", UriKind.Relative) 
};

for (int i = 0; i < labels.Count; i++)
{
    labels[i].Style = (Style) skin["labelStyle"];
}