Changing the styles at runtime in WPF

Question

I am trying to allow the user to customize the elements in a WPF application. What I am trying to achieve is, if I have a list box which specifies all the form elements (Tex

Answer 1

it worked for me like a charm:

Xaml:

<TreeView x:Name="TreePeople">
    <TreeView.ItemContainerStyle>
        <Style TargetType="{x:Type TreeViewItem}">
            <Setter Property="IsExpanded" Value="True" />
        </Style>
    </TreeView.ItemContainerStyle>
</TreeView> 

c#:

bool Expanded = false; 
// The event subscription method (for a button click)
private void ButtonExpand__Click(object sender, RoutedEventArgs e)
{
    Expanded = !Expanded;
    Style Style = new Style
    {
        TargetType = typeof(TreeViewItem)
    };

    Style.Setters.Add(new Setter(TreeViewItem.IsExpandedProperty, Expanded));
    TreePeople.ItemContainerStyle = Style;
}

Answer 2

Have you tried using Resource Dictionaries

Resource Dictionary

<ResourceDictionary
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<SolidColorBrush x:Key="TextColor" Color="#FF121212"/>
</ResourceDictionary>

XAML for the control

<TextBox Text="TextBox" Foreground="{DynamicResource TextColor}" />

Code to change styles at runtime

     var rd = new ResourceDictionary();
     rd.Add("TextColor", "#FFFFFF");
     Application.Current.Resources.MergedDictionaries.Add(rd);

This will merge your new styles with the existing ones, and the change will be automatically reflected on all the controls linked with those styles.

Answer 3

You have to make sure that the styles are in the file App.xaml:

<Application x:Class="ChangeStyleHelp.App"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         StartupUri="MainWindow.xaml">

    <Application.Resources>
        <Style x:Key="MyStyle" TargetType="{x:Type Label}">
            <Setter Property="Background" Value="Green" />
        </Style>
    </Application.Resources>
</Application>

Code behind:

private void ChangeStyle_Click(object sender, RoutedEventArgs e)
{
    Style style = new Style 
    { 
        TargetType = typeof(Label) 
    };

    style.Setters.Add(new Setter(Label.BackgroundProperty, Brushes.Aquamarine));

    Application.Current.Resources["MyStyle"] = style;
}   

If the Style is in the resource of Window (Window.Resources), then you need to write this, or the name of the Window:

private void ChangeStyle_Click(object sender, RoutedEventArgs e)
{
    Style style = new Style 
    { 
        TargetType = typeof(Label) 
    };

    style.Setters.Add(new Setter(Label.BackgroundProperty, Brushes.Aquamarine));

    this.Resources["MyStyle"] = style;
}   

As well, you can change the Style this way: take an existing style and use of the element. Example:

<Application x:Class="ChangeStyleHelp.App"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         StartupUri="MainWindow.xaml">

    <Application.Resources>
        <Style x:Key="AnotherWayStyle" TargetType="{x:Type Label}">
            <Setter Property="Background" Value="Lavender" />
            <Setter Property="Foreground" Value="OrangeRed" />
        </Style>
    </Application.Resources>
</Application>  

Code behind:

private void AnotherWay_Click(object sender, RoutedEventArgs e)
{
    label1.Style = (Style)Application.Current.Resources["AnotherWayStyle"];
}