How to make a text box Visibility=Hidden with a trigger

Question

I seem to be having a hard time today. All I want to do is make a TextBox hidden of visible based on a bool value databound to the Window its hosted in.

What I have just won't compile and I don't understand why. Please help.

<TextBlock Grid.Column="2" Text="This order will be sent to accounting for approval" 
           Foreground="Red" VerticalAlignment="Center" FontWeight="Bold" Padding="5">
    <TextBlock.Style>
        <Style>
            <Style.Triggers>
                <DataTrigger Binding="{Binding Path=AllowedToSubmit}" Value="True">
                    <Setter Property="Visibility" Value="Hidden" /> 
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </TextBlock.Style>
</TextBlock>

Solution 1

You need to set the Style.TargetType in order for it to recognize the Visibility property:

<TextBlock Grid.Column="2" VerticalAlignment="Center" FontWeight="Bold" Foreground="Red" Padding="5" Text="This order will be sent to accounting for approval">
    <TextBlock.Style>
        <Style TargetType="{x:Type TextBlock}">
            <Style.Triggers>
                <DataTrigger Binding="{Binding Path=AllowedToSubmit}" Value="True">
                    <Setter Property="Visibility" Value="Hidden"/>
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </TextBlock.Style>
</TextBlock>

Your binding path to AllowedToSubmit probably needs to have ElementName set to the Window's name, as well.

Solution 2

Another option is to bind TextBlock.Visibility directly to the property:

<Window>
    <Window.Resources>
        <BooleanToVisibilityConverter x:Key="BoolToVisibility" />
    </Window.Resources>
    <TextBlock Visibility="{Binding Path=AllowedToSubmit, Converter={StaticResource BoolToVisibility}}" />
</Window>

If you want it to work like in your sample, where true hides the TextBlock, then you can write your own converter to convert opposite of the built-in BooleanToVisibilityConverter.

Comments

[Andy]

Not necessarily - he might have set a DataContext further up the tree, and AllowedToSubmit is a property on that object.

[Adrian]

Agreed with Andy. If Russ is using MVVM, he probably has a DataContext to resolve the binding.

[Russ]

MVVM. I don't need to set the ElementName. Thanks for the tip though. My years of winforms is proving to be pretty worthless in WPF. :)

[Sergey Aldoukhov]

Looks like a style within control TargetType could be defaulted to the owner, not sure why MS didn't do this... Any ideas?

[Robert Macnee]

Good call about not needing the ElementName, I'll remove that part of the answer. re: Default TargetType, if the Style were sitting as a resource you'd get the same error, since it could be assigned to anything it needs to know what it will be ahead of time.

[Michi-2142]

This is the most common way to set the visibility in WPF using MVVM. +1

[MwBakker]

Except if the property field changes during the presentation of the view, it won't change visibility