Question

Why would my VisualBrush render a lovely image in my button with this code:

<Button>
    <Rectangle Width="28" Height="28">
        <Rectangle.Fill>
            <VisualBrush Stretch="Fill" Visual="{StaticResource lovely_image}" />
        </Rectangle.Fill>
    </Rectangle>
</Button>

But render nothing with this code?:

<Button>
    <Rectangle Width="28" Height="28">
        <Rectangle.Style>
            <Style TargetType="{x:Type Rectangle}">
               <Setter Property="Fill">
                    <Setter.Value>
                        <VisualBrush Stretch="Fill" Visual="{StaticResource lovely_image}" />                               
                    </Setter.Value>
                </Setter>
            </Style>
        </Rectangle.Style>
    </Rectangle>
</Button>

Interestingly, if I replace the VisualBrush in the second example with a SolidColorBrush, the SolidColorBrush renders.

(Why am I doing this? I’m trying to use DataTriggers to swap icons based on values in my ViewModel.)

Update

So it seems that this code works just fine. My problem was actually some weirdness in the way my resources which define my visual. The visual used a brush dynamic resource which was being loaded from a referenced assembly. This worked with the first example above, but for some reason wouldn’t for the second example. I just copied the brush into a resource in my projects assembly and viola!, my lovely_image is rendered.

Answer 1

A SolidColorBrush is abstract and can be used in multiple places. A visual is not, it can only have one parent.

You can try x:Shared="false" on the visual in the resources. Or use the Button.ContentTemplate to make the button create multiple Rectangles (inline the visual & Content needs to be set to something for it to apply).

Also if this is not about multiple instances as the code in your question is fine: Mind dependency property value precedence.