Wpf – Display validation error in DataGridCell tooltip

datagridwpf

I have a WPF DataGrid which displays types that implement IDataErrorInfo. As expected when the validation fails the row gets the red exclamation mark and the invalid cell gets the red highlight.
enter image description here

This is all well and good; however, I want the validation error message to display in the tooltip of the invalid cell so the user has some indication of what is wrong. I presently have:

<DataGrid.CellStyle>
    <Style TargetType="DataGridCell">
        <Setter Property="ToolTip"
                Value="{Binding RelativeSource={RelativeSource Self},
                                                Path=(Validation.Errors[0].ErrorContent}"/>
     </Style>
</DataGrid.CellStyle>

This approach works for TextBox but not for DataGridCell. What is the difference?

Best Answer

I have something similiar in a project I'm working on right now, and it goes something like this:

<DataGridTextColumn.ElementStyle>
    <Style TargetType="{x:Type TextBlock}">
        <Setter Property="DataGridCell.ToolTip"
                Value="{Binding RelativeSource={RelativeSource Self},
                                                Path=(Validation.Errors)[0].ErrorContent}"/>
     </Style>
</DataGridTextColumn.ElementStyle>

Related Solutions

WPF Datagrid Cell with Validation Error Style

Try this:

<!-- Cell Style -->
    <Style x:Key="CellErrorStyle" TargetType="{x:Type TextBlock}">
        <Style.Triggers>
            <Trigger Property="Validation.HasError" Value="true">
                <Setter Property="ToolTip"
                        Value="{Binding RelativeSource={RelativeSource Self},
                                Path=(Validation.Errors)[0].ErrorContent}"/>
                <Setter Property="Background" Value="Yellow"/>
            </Trigger>
        </Style.Triggers>
    </Style>

And use it:

        <DataGrid.Columns>
            <DataGridTextColumn 
                ElementStyle="{StaticResource CellErrorStyle}">
            </DataGridTextColumn>
        </DataGrid.Columns>

Wpf – Validation ErrorTemplate not showing on data errors

Cracked it.

The ErrorTemplate attached property uses the adorner layer to show error templates on data validation failures reported via IDataErrorInfo. The Adorner layer is not always available for all controls in all situations. Your control or one of its parents needs to explicitly provide one.

The default Window control template contains an AdornerDecorator which enables the adorner layer for its children. This why my other window showed my error templates just fine, because this window used the default control template

The window which didn't show my error template had used a style which provided a ControlTemplate for my window. This control template did not provide an <AdornerDecorator>, hence no adorner layer to show my error template.

The fix was as simple as wrapping my window control template with <AdornerDecorator>.

Best Answer

Related Solutions

WPF Datagrid Cell with Validation Error Style

Wpf – Validation ErrorTemplate not showing on data errors

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