How can I change an elements style at runtime?

Question

I have an element and multiple styles, how do I switch between the styles at runtime either programatically or through XAML binding.

<Rectangle x:Name="fixtureControl" Style="{DynamicResource FixtureStyle_Fast}">

<!-- In the style resources. -->
<Style x:Key="FixtureStyle_Fast" TargetType="{x:Type Shape}">
    <Setter Property="Stroke" Value="Black"/>
    <Setter Property="StrokeThickness" Value="20"/>
</Style>

<Style x:Key="FixtureStyle_Good" TargetType="{x:Type Shape}">
    <Setter Property="Effect">
        <Setter.Value>
            <DropShadowEffect Opacity=".9"
                              Direction="-90"
                              RenderingBias="Performance"
                              BlurRadius="50"
                              ShadowDepth="10" />
        </Setter.Value>
    </Setter>
</Style>

<Style x:Key="FixtureStyle_Best" TargetType="{x:Type Shape}">
    <Setter Property="Effect">
        <Setter.Value>
            <DropShadowEffect Opacity=".9"
                              Direction="-90"
                              RenderingBias="Quality"
                              BlurRadius="50"
                              ShadowDepth="10" />
        </Setter.Value>
    </Setter>
</Style>

Then I have some radio buttons that handle changing the style

private void RadioButton_Click(object sender, RoutedEventArgs e) {
    if (e.Source == rdoQualityBest) {
        fixtureControl.Style = FindResource("FixtureStyle_Best") as Style;
    } else if (e.Source == rdoQualityGood) {
        fixtureControl.Style = FindResource("FixtureStyle_Good") as Style;
    } else {
        fixtureControl.Style = FindResource("FixtureStyle_Fast") as Style;
    }
}

However this applies the style to the element, not replacing it, so if I apply Fast then Quality, I get both the border and the drop-shadow.

Answer 1

It is working fine for me

here is my code:

in .xaml

    <Window.Resources>
    <Style x:Key="FixtureStyle_Fast" TargetType="{x:Type Shape}">
        <Setter Property="Stroke" Value="Black"/>
        <Setter Property="StrokeThickness" Value="20"/>
    </Style>

    <Style x:Key="FixtureStyle_Good" TargetType="{x:Type Shape}">
        <Setter Property="Stroke" Value="Red"/>
        <Setter Property="StrokeThickness" Value="20"/>
    </Style>

    <Style x:Key="FixtureStyle_Best" TargetType="{x:Type Shape}">
        <Setter Property="Stroke" Value="Blue"/>
        <Setter Property="StrokeThickness" Value="20"/>
    </Style>
</Window.Resources>
<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition/>
        <ColumnDefinition/>
    </Grid.ColumnDefinitions>
     <Rectangle x:Name="fixtureControl" Style="{DynamicResource FixtureStyle_Fast}"/>
    <StackPanel Grid.Column="1">
    <RadioButton Name="rdoQualityBest" Content="Best" Click="RadioButton_Click" />
    <RadioButton Name="rdoQualityGood" Content="Good" Click="RadioButton_Click" />
    <RadioButton Name="rdoQualityFast" Content="Fast" Click="RadioButton_Click" />
    </StackPanel>
</Grid>

in .xaml.cs

private void RadioButton_Click(object sender, RoutedEventArgs e)
{
    if (e.Source == rdoQualityBest)
    {
        fixtureControl.Style = FindResource("FixtureStyle_Best") as Style;
    }
    else if (e.Source == rdoQualityGood)
    {
        fixtureControl.Style = FindResource("FixtureStyle_Good") as Style;
    }
    else
    {
        fixtureControl.Style = FindResource("FixtureStyle_Fast") as Style;
    }
}

Answer 2

Something like this has worked for me in the past (a pure XAML solution):

<!-- Styles 1-4 defined somewhere else on your page -->
<ComboBox Name="AvailableStyles">
    <ComboBoxItem Tag="{x:Null}" IsSelected="True">None</ComboBoxItem>
    <ComboBoxItem Tag="{StaticResource Style1}">1</ComboBoxItem>
    <ComboBoxItem Tag="{StaticResource Style2}">2</ComboBoxItem>
    <ComboBoxItem Tag="{StaticResource Style3}">3</ComboBoxItem>
    <ComboBoxItem Tag="{StaticResource Style4}">4</ComboBoxItem>
</ComboBox>

<Button Content="Button" Style="{Binding ElementName=AvailableStyles, Path=SelectedItem.Tag}"/>
<CheckBox Content="Check Box" Style="{Binding ElementName=AvailableStyles, Path=SelectedItem.Tag}"/>
<RadioButton Content="Radio Button"Style="{Binding ElementName=AvailableStyles, Path=SelectedItem.Tag}"/>

Hope this helps!