wpf - Validation.Error 事件的奇怪触发顺序 - 添加在删除之前触发

Question

就 Validation.Error 事件的触发顺序而言，我遇到了奇怪的行为。根据文档here , 数据绑定(bind)引擎首先删除可能已添加到绑定(bind)元素的 Validation.Errors 附加属性中的任何 ValidationError。因此，Removed 的 ValidationErrorEvent 应该在 Added 之前触发，但奇怪的是，在我的情况下，Added 事件在 之前触发删除事件。这是我正在使用的代码。

XAML

<TextBox Grid.Row="3" Grid.Column="1" Name="txtGroupsPerRow" >
    <TextBox.Text>
        <Binding Path="StandardRack.NoOfGroupsPerRow" ValidatesOnDataErrors="True" NotifyOnValidationError="True" 
                 UpdateSourceTrigger="PropertyChanged">
            <Binding.ValidationRules>
                <gs:NumericValidationRule PropertyName="No Of Groups Per Row"/>
            </Binding.ValidationRules>
        </Binding> 
    </TextBox.Text>
</TextBox>

代码隐藏

private RoutedEventHandler _errorEventRoutedEventHandler;
private void UserControl_Loaded(object sender, RoutedEventArgs e) {
    _errorEventRoutedEventHandler = new RoutedEventHandler(ExceptionValidationErrorHandler);
    this.AddHandler(System.Windows.Controls.Validation.ErrorEvent, _errorEventRoutedEventHandler, true); 
}

private void UserControl_Unloaded(object sender, RoutedEventArgs e) {
    this.RemoveHandler(System.Windows.Controls.Validation.ErrorEvent, _errorEventRoutedEventHandler);
    _errorEventRoutedEventHandler = null;
}

//Added fired before Removed
private void ExceptionValidationErrorHandler(object sender, RoutedEventArgs e) {
    if (validationErrorEvent.Action == ValidationErrorEventAction.Added) {
        viewModel.AddValidationError(propertyPath, validationErrorEvent.Error.ErrorContent.ToString());
    }
    else if (validationErrorEvent.Action == ValidationErrorEventAction.Removed) {
        viewModel.RemoveValidationError(propertyPath);
    }
}

有没有人遇到过这个问题，或者我的代码有什么问题？

Answer 1

查看 source code , 在删除旧验证错误之前添加新验证错误的步骤

are carefully ordered to avoid going through a "no error" state while replacing one error with another