Question

As the title says, I have a hidden border with some controls inside, and I would like to show it when a particular item in a combobox is selected.

I tried the following

<ComboBox Name="cmbRequiredRule" SelectedValuePath="Content"                                                                                                    
          SelectedValue="{Binding Path=ClientValidation.NarrativeRequiredRule}">
    <ComboBoxItem>All</ComboBoxItem>                         
    <ComboBoxItem>Matching</ComboBoxItem>
</ComboBox>

<Border Visibility="Collapsed">
    <Border.Resources>
        <Style TargetType="{x:Type Border}">
            <Style.Triggers>
                <DataTrigger Binding="{Binding Path=ClientValidation.NarrativeRequiredRule}" Value="Matching">
                    <Setter Property="Visibility" Value="Visible" />
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </Border.Resources> 
.... 
</Border>

and this property in the view model:

 public string NarrativeRequiredRule
    {
        get... 
        set... 
    } 

but the trigger doesn’t seem to be working

Answer 1

Try setting Visibility=Collapsed in your Style Setters, not as part of the Border Tag. I’ve had issues in the past where a DataTrigger would not apply when the value was specified as part of the Tag.

    <Border>
        <Border.Resources>
            <Style TargetType="{x:Type Border}">
                <Setter Property="Visibility" Value="Collapsed" />
                <Style.Triggers>
                    <DataTrigger Binding="{Binding Path=Test}" Value="Matching">
                        <Setter Property="Visibility" Value="Visible" />
                    </DataTrigger>
                </Style.Triggers>
            </Style>
        </Border.Resources>
        ...
    </Border>