How can I indicate in the Expander header that the collapsed content has an error
I have expanders that contain textboxes, textboxes use wpf validation stuff to draw a red border around them (textboxes are wrapped in Adorner Decorators to make sure I don't get empty red boxes all over the place when the expanders collapse)
I want to indicate in the header of the expander that it has content that has errors (in case it is folded) - an icon or a red exclamation mark or whatever. I think I can see a way to do this in code from within my validation function (not perfect), but is there a way to do this in xaml? Can I style the expander with a trigger somehow pointing to Validation.HasError for all children?
thanks for any thoughts ..
Trev
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If you know the content of your expander, you can use a MultiDataTrigger to do this:
<Expander>
<Expander.Header>
<TextBlock>
<TextBlock.Style>
<Style TargetType="{x:Type TextBlock}">
<Setter Property="Text" Value="ERROR"/>
<Style.Triggers>
<MultiDataTrigger>
<MultiDataTrigger.Conditions>
<Condition Binding="{Binding ElementName=txtWidth, Path=(Validation.HasError)}" Value="False"/>
<Condition Binding="{Binding ElementName=txtHeight, Path=(Validation.HasError)}" Value="False"/>
</MultiDataTrigger.Conditions>
<Setter Property="Text" Value="NO ERROR"/>
</MultiDataTrigger>
</Style.Triggers>
</Style>
</TextBlock.Style>
</TextBlock>
</Expander.Header>
<StackPanel>
<TextBox x:Name="txtWidth" Text="{Binding Width, ElementName=rect, UpdateSourceTrigger=PropertyChanged, ValidatesOnExceptions=True}"/>
<TextBox x:Name="txtHeight" Text="{Binding Height, ElementName=rect, UpdateSourceTrigger=PropertyChanged, ValidatesOnExceptions=True}"/>
<Rectangle x:Name="rect" Width="100" Height="100" Margin="10" Fill="Green"/>
</StackPanel>
</Expander>
If you don't know the content of the extender, you probably have to set the Binding.NotifyOnValidationError to the TextBoxes and handle the error event.
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