Using MultiDataTrigger.Condition from the Settings class

Question

My MultiDataTrigger should change the properties of a TabItem if both values are as expected. One of the values is a Property from the TabItem , the other one is a Properties.Settings.Default property.

<!--<App xmlns:prop="clr-namespace:MyApp.Properties"... -->

<DropShadowEffect x:Key="Glow.Foreground.Large" ShadowDepth="0" Color="WhiteSmoke" 
                  Opacity="1" BlurRadius="10" RenderingBias="Quality"/>

<Style TargetType="{x:Type TabItem}">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type TabItem}">
                <Grid Name="Panel" Background="Transparent">
                    <Border Name="ContentBorder" 
                            BorderBrush="#FFD4D4D4" BorderThickness="0">
                        <ContentPresenter x:Name="ContentSite"
                            VerticalAlignment="Center" Effect="{x:Null}"
                            HorizontalAlignment="Center"
                            ContentSource="Header"
                            Margin="10,2"/>
                            </Border>
                    </Grid>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsSelected" Value="True">
                            <Setter TargetName="Panel" 
                                    Property="Background" 
                                    Value="#FFFAFAFA" />
                            <Setter Property="Foreground"
                                    Value="#FF2B579A" />
                            <Setter TargetName="ContentBorder"
                                    Property="BorderThickness" 
                                    Value="1,1,1,0" />
                            </Trigger>
                        <MultiDataTrigger>
                            <MultiDataTrigger.Conditions>
                                <Condition Property="IsSelected" Value="False"/>
                                <Condition Binding="{Binding 
                                           Source={x:Static prop:Settings.Default}, 
                                           Path=EditorExtendChrome}" Value="True"/>
                            </MultiDataTrigger.Conditions>

                            <Setter TargetName="ContentBorder"
                                    Property="Effect" 
                                    Value="{StaticResource Glow.Foreground.Large}" />
                            <Setter TargetName="ContentBorder"
                                    Property="Background" 
                                    Value="#7FFFFFFF"/>
                        </MultiDataTrigger>
                        <Trigger Property="IsMouseOver" Value="True"
                                 SourceName="Panel">
                            <Setter Property="Foreground"
                                    Value="#FF2B579A" />
                            <Setter Property="Background"
                                    Value="#FFFAFAFA" />
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>

        <!--Default Values-->
        <Setter Property="FontFamily" Value="Segoe UI Semilight"/>
    </Style>

I'm following this post , yet the error "You must have a non-null value for 'Binding'" stills persists.

Answer 1

The normal Settings class does not provide WPF-compatible property change notifications. It's likely that's why your code doesn't work. But without a good, minimal , complete code example that reliably reproduces the problem, there is no way to know for sure.

The Default property will be null early in the execution of the program, and so without property change notifications, WPF will only have ever seen the null value, which of course is of no use to it.

Also note that, per the SO answer you're referencing, the Condition object for a MultiDataTrigger should specify Binding and not Property .

If the above does not address your concern, please provide a better code example and also be more specific about the error: when do you see this error, how is it reported, and what is the full stack trace for the error (if available)? Note that with a good code example, then even without direct support for property change notifications, it's possible an answer that solves your exact scenario could be provided.