Question

I have a textbox that a user puts a server name into, and it’s validated as an FQDN as he types. I also have a style that gets applied when the validation fails that makes the background of the textbox pink. However, I don’t want this to happen when high contrast mode is on and I can’t really seem to find much literature on how to accomplish this.

Here’s the textbox/style:

<TextBox ...>
    <TextBox.Style>
        <Style>
            <Style.Triggers>
                <DataTrigger Binding="{Binding ServerName.HasErrorsToShow}" Value="true">
                    <Setter Property="TextBox.Background" Value="Pink" />
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </TextBox.Style>
</TextBox>

How can I accomplish this? Thanks!

EDIT 1:

I tried using a MultiTrigger. It seems promising, but I can’t quite get it right. This chunk of code worked (for testing whether I could base decisions on high contrast):

<Style.Triggers>
    <DataTrigger Binding="{Binding Source={x:Static SystemParameters.HighContrast}}" Value="True">
        <Setter Property="TextBox.Background" Value="Pink" />
    </DataTrigger>
</Style.Triggers>

But when I tried adding the MultiTrigger, I got a “Set property ‘System.Windows.FrameworkElement.Style’ threw an exception” exception. The inner exception was “Must have non-null value for ‘Property'”. Here’s the code for that:

<Style.Triggers>
    <MultiTrigger>
        <MultiTrigger.Conditions>
            <Condition Binding="{Binding ServerName.HasErrorsToShow}" Value="True" />
            <Condition Binding="{Binding Source={x:Static SystemParameters.HighContrast}}" Value="False" />
        </MultiTrigger.Conditions>
        <Setter Property="TextBox.Background" Value="Pink" />
    </MultiTrigger>
</Style.Triggers>

Answer 1

I haven’t tested this code out, but perhaps you could use a MultiTrigger and bind to the HighContrast property of the SystemParameters object. Something like this:

[removed, see below]

Note: I’m pretty sure the HighContrast property of the static SystemParameters class is not a dependency property, and won’t raise NotifyPropertyChanged, so if the user changes the setting while the application is already open, I don’t believe the trigger will fire.

Edit:
This style seems to do the job for me.

<Style x:Key="MyTextBoxStyle" TargetType="{x:Type TextBox}">
  <Setter Property="Tag" Value="{DynamicResource {x:Static SystemParameters.HighContrastKey}}"/>
  <Setter Property="Background" Value="Green"/>
  <Style.Triggers>
    <MultiDataTrigger>
        <MultiDataTrigger.Conditions>
            <Condition Binding="{Binding ServerName.HasErrorsToShow}" Value="true"/>
            <Condition  Binding="{Binding RelativeSource={RelativeSource Self}, Path=Tag}" Value="True"/>
        </MultiDataTrigger.Conditions>
        <Setter Property="Background" Value="Red"/>
    </MultiDataTrigger>
  </Style.Triggers>
</Style>