How to 'Disable' a WPF UserControl?

Question

I have a UserControl, and I need to change its appearance when 'IsEnabled' is false. I know this is pretty basic WPF styling, but I can't seem to put the pieces together. I assume that I need to create a Style, and add a trigger for "Property="IsEnabled" Value="False". But where do I put the Style definition? (<UserControl.Resources>?) How do I apply it? ... in the UserControl or in the Parent window? Does my trigger need to be inside a Setter element? Does the style need to be applied to the UserControl or to its children? I don't know what other questions I need to ask!

If you feel this is a duplicate of another question, please direct me to it. If you know of a good, simple tutorial on WPF styling that would answer my questions, I would be very grateful to hear of it.

My code looks like this:

<UserControl x:Class="UserControls.UCDemo"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         xmlns:local="clr-namespace:UserControls"
         mc:Ignorable="d" 
         d:DesignHeight="240" d:DesignWidth="200">
<UserControl.Resources>

</UserControl.Resources>

<Grid Background="Transparent">
    <Grid.RowDefinitions>
        <RowDefinition Height="5*" />
        <RowDefinition Height="*" />
    </Grid.RowDefinitions>
    <Grid Grid.Row="0" Background="{Binding BG}" >
        <Ellipse Grid.Row="0" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Margin="5" Fill="DeepSkyBlue" />
    </Grid>
    <Grid Grid.Row="1" Background="Tomato" />
</Grid>

        <uc:UCDemo x:Name="Demo" HorizontalAlignment="Left" VerticalAlignment="Top" Margin="300,100,0,0" Width="80" Height="100" Style="{StaticResource uc:DemoStyle}"
                        Visibility="{Binding LightVisible, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}, Converter={StaticResource BooleanToVisibilityConverter}}" />

Thank you for your help!

Answer 1

It depends on how exactly the appearance should change when IsEnabled is false.

A simple Style with a Trigger could be assigned directly to the UserControl's Style property. The one below just sets the Opacity to 0.5.

<UserControl ...>
    <UserControl.Style>
        <Style TargetType="UserControl">
            <Style.Triggers>
                <Trigger Property="IsEnabled" Value="False">
                    <Setter Property="Opacity" Value="0.5"/>
                </Trigger>
            </Style.Triggers>
        </Style>
    </UserControl.Style>

    <Grid Background="Transparent">
        ...
    </Grid>
</UserControl>

Answer 2

I'm not sure I get what your question is. However in order to change the IsEnabled property of a control, depending on an other controls is: Let's suppose that the control which its IsEnabled must be changed, is A and the control which A is depends on, is B. First, choose a name for B: x:Name = "AccessCheckBox" . Then Write a binding like this for control B:

< ... IsEnabled = {Binding ElementName = "AccessCheckBox", Path="IsChecked".../>

Done. I hope I got what you mean.