Question

It took me hours to figure out the answer to this question, so I thought I would write an FAQ or answer for what I found. (it is based on the following thread Binding Textbox IsFocused to Popup IsOpen plus additional conditions)

I found lots of examples of binding popups to things like toggle buttons and other things that are based on windows chrome and have built in triggers. But in my application I wanted to bind a popup to a simple rectangle with a custom brush fill. I could not find an example on how to have a popup open ans stay open when a user mouses over the rectangle.

So I am posting this question and I will immediately post the answer I found so that hopefully someone else can benefit from it. I will also mark an answer for anyone who can help me understand if stackoverflow allows posts like this, or a better way I could have gone about it.

EDIT 1)

I can’t self answer for 8 hours so here is the working code:
the following is a simple example of how to use the popup on a basic UIElement like a rectangle/ellipse/etc…

<Grid HorizontalAlignment="Stretch" Height="Auto">
    <Rectangle x:Name="PopupRec"
               Grid.Row="0"
               Width="20" Height="20"
               HorizontalAlignment="Right" 
               Fill="Gray" Margin="0,0,0,10" />
    <Popup x:Name="SortPopup" 
           PlacementTarget="{Binding ElementName=PopupRec}" 
           StaysOpen="False" 
           PopupAnimation="Slide" 
           AllowsTransparency="True">
        <Border Background="White" Padding="15">
            <StackPanel Orientation="Vertical">
                <Button Command="{Binding MyCommand}" CommandParameter="5">5</Button>
                <Button Command="{Binding MyCommand}" CommandParameter="10">10</Button>
                <Button Command="{Binding MyCommand}" CommandParameter="15">15</Button>
                <Button Command="{Binding MyCommand}" CommandParameter="20">20</Button>
            </StackPanel>
        </Border>
        <Popup.Style>
            <Style TargetType="{x:Type Popup}">
                <Style.Triggers>
                    <DataTrigger Binding="{Binding ElementName=PopupRec, Path=IsMouseOver}" Value="True">
                        <Setter Property="IsOpen" Value="True" />
                    </DataTrigger>
                    <DataTrigger Binding="{Binding ElementName=SortPopup, Path=IsMouseOver}" Value="True">
                        <Setter Property="IsOpen" Value="True" />
                    </DataTrigger>
                </Style.Triggers>
            </Style>
        </Popup.Style>
    </Popup>
</Grid>

Just paste this inside window/usercontrol/etc…

Answer 1

I’d suggest the following improvement. It would make the Popup Style independent of any element names, and would thus enable you to use it as a default Style by putting it into the Window’s or UserControl’s Resources.

<Style TargetType="{x:Type Popup}">
    <Style.Triggers>
        <DataTrigger Binding="{Binding Path=IsMouseOver,
                               RelativeSource={RelativeSource Self}}"
                     Value="True">
            <Setter Property="IsOpen" Value="True" />
        </DataTrigger>
        <DataTrigger Binding="{Binding Path=PlacementTarget.IsMouseOver,
                               RelativeSource={RelativeSource Self}}"
                     Value="True">
            <Setter Property="IsOpen" Value="True" />
        </DataTrigger>
    </Style.Triggers>
</Style>

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And please note that a Rectangle is not a “basic UIElement”. It’s a Shape, which itself is a FrameworkElement.