WPF DataGrid validation errors not clearing

Question

So I have a WPF DataGrid, which is bound to an ObservableCollection. The collection has validation on its members, through IDataErrorInfo. If I edit a cell in a way so as to be invalid, and then tab away from it before hitting enter, then come back and make it valid, the cell will stop showing invalid, however, the "!" at the head of the row will still be there, and the ToolTip will reference the previous, invalid value.

Answer 1

I found best answer that worked for me. Just clear your DataGrid's RowValidationErrorTemplate.

1. In Code

   YourGrid.RowValidationErrorTemplate = new ControlTemplate();
   

2. In Xaml

   <DataGrid.RowValidationErrorTemplate>
       <ControlTemplate>
       </ControlTemplate>
   </DataGrid.RowValidationErrorTemplate>`
   

3. Then make your own Row Validation Error Template.

   If your data item is INotifyPropertyChanged

   ((INotifyPropertyChanged)i).PropertyChanged += this.i_PropertyChanged;`
   

   then

   private void i_PropertyChanged(object sender, PropertyChangedEventArgs e)
   {
       this.Dispatcher.BeginInvoke(new Action(() =>
       {
           var row = this.ItemContainerGenerator.ContainerFromItem(sender) as DataGridRow;
           if (row == null)
               return;
   
           var Errs = IsValid(row);
   
           if (Errs.Count == 0) row.Header = null;
           else
           {
               // Creatr error template
               var gg = new Grid { ToolTip = "Error Tooltip" };
   
               var els = new Ellipse { Fill = new SolidColorBrush(Colors.Red), Width = row.FontSize, Height = row.FontSize };
   
               var tb = new TextBlock
               {
                   Text = "!",
                   Foreground = new SolidColorBrush(Colors.White),
                   HorizontalAlignment = HorizontalAlignment.Center,
                   FontWeight = FontWeights.Bold
               };
   
               gg.Children.Add(els);
               gg.Children.Add(tb);
   
               row.Header = gg;
           }
       }),
        System.Windows.Threading.DispatcherPriority.ApplicationIdle);
   }
   

4. Write your own IsValid method, the way you like

Answer 2

I have the same problem with the RowHeader error template not going away. I am using INotifyDataErrorInfo. Following up on the research by Fredrik Hedblad I have made a workaround; I have modified the DataGridRowHeader template to use a MultiBinding for the ValidationErrorTemplate visibility:

  <Style x:Key="DataGridRowHeaderStyle" TargetType="{x:Type DataGridRowHeader}">
<!--<Setter Property="Background" Value="{DynamicResource {ComponentResourceKey TypeInTargetAssembly=Brushes:BrushesLibrary1,
             ResourceId=HeaderBrush}}"/>-->
<Setter Property="Template">
  <Setter.Value>
    <ControlTemplate TargetType="{x:Type DataGridRowHeader}">
      <Grid>
        <Microsoft_Windows_Themes:DataGridHeaderBorder BorderBrush="{TemplateBinding BorderBrush}"
                          BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}"
                          IsPressed="{TemplateBinding IsPressed}" IsHovered="{TemplateBinding IsMouseOver}"
                            IsSelected="{TemplateBinding IsRowSelected}" Orientation="Horizontal"
                            Padding="{TemplateBinding Padding}" SeparatorBrush="{TemplateBinding SeparatorBrush}"
                            SeparatorVisibility="{TemplateBinding SeparatorVisibility}">
          <StackPanel Orientation="Horizontal">
            <ContentPresenter SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="Center"
                                                                Width="15"/>
            <Control SnapsToDevicePixels="false"
                                       Template="{Binding ValidationErrorTemplate, RelativeSource={RelativeSource AncestorType={x:Type DataGridRow}}}">
              <Control.Visibility>
              <MultiBinding Converter="{StaticResource ValidationConverter}">
                <Binding Path="(Validation.HasError)" RelativeSource="{RelativeSource AncestorType={x:Type DataGridRow}}"/>
                <Binding Path="DataContext.HasErrors" RelativeSource="{RelativeSource AncestorType={x:Type DataGridRow}}"/>
              </MultiBinding>
              </Control.Visibility>
              <!-- Original binding below -->
              <!--Visibility="{Binding (Validation.HasError), Converter={StaticResource bool2VisibilityConverter},
                     RelativeSource={RelativeSource AncestorType={x:Type DataGridRow}}}">-->
            </Control>
          </StackPanel>
        </Microsoft_Windows_Themes:DataGridHeaderBorder>
        <Thumb x:Name="PART_TopHeaderGripper" Style="{StaticResource RowHeaderGripperStyle}" VerticalAlignment="Top"/>
        <Thumb x:Name="PART_BottomHeaderGripper" Style="{StaticResource RowHeaderGripperStyle}" VerticalAlignment="Bottom"/>
      </Grid>
    </ControlTemplate>
  </Setter.Value>
</Setter>

This relies on the bound objects having a "HasErrors" property with change notification. In my project I have ensured that the HasErrors property is updated by raising the PropertyChanged for HasErrors in the item EndEdit event.