WPF TextBox验证异常：边框变色后卡顿/占位符重叠问题求助

需求：TextBox输入商品编号（artikelnummer），若该编号对应的记录超过6个月，将TextBox边框设为红色，需通过SQL查询获取数据，业务逻辑已验证正确，但UI实现存在问题，尝试三种方案均异常：

方案1：TextChange事件实现 #

代码：

TextBox tbx = sender as TextBox;

if (tbx.Text.Length > 7)
{
    string getDate = SQL;
    try
    {
        using (var reader = command.ExecuteReader())
        {
            if (reader.HasRows)
            {
                reader.Read();
                date = reader.GetDateTime(0);

            }
            reader.Close();
        }

        var lastmonth = DateTime.Today.AddMonths(-6);

        if (lastmonth < date)
        {
            tbx.BorderBrush = (Brush)Application.Current.MainWindow.FindResource("BorderBrushWrong");
        }
        else
        {
            tbx.BorderBrush = (Brush)Application.Current.MainWindow.FindResource("BorderBrush");
        }


    }
    catch
    {
        
    }
}

问题：边框变红后，TextBox控件卡顿，无法正常切换焦点、选中文字，仅能通过删除键清除内容。

方案2：绑定属性+DataTrigger实现 #

属性代码：

private string _TopArtikel;
public string TopArtikel
{
    get
    {
        //replaceHTMLnew();
        return _TopArtikel;

    }
    set
    {
        _TopArtikel = value;
        inputCheck(_TopArtikel);
        NotifyPropertyChanged(nameof(TopArtikel));
    }
}

inputCheck中设置colorcheck = true;，Style中添加DataTrigger：

<DataTrigger Binding="{Binding colorcheck}" Value="True">
    <Setter Property="BorderBrush" Value="Red"/>
</DataTrigger>

问题：出现与第一种方案相同的卡顿现象。

方案3：ValidationRule实现 #

验证类代码：

public override ValidationResult Validate(object value, CultureInfo cultureInfo)
{
    NewsViewModel viewModel = new NewsViewModel();
    string input = value.ToString();
    if (input.Length > 7)
    {
        string getDate = SQL;

        DateTime date = new DateTime();

        IGenericCommand command = viewModel.mandant.MainDevice.GenericConnection.CreateSqlStringCommand(getDate);

        command.AppendInParameter("artikelnummer", typeof(string), input);
        try
        {
            using (var reader = command.ExecuteReader())
            {
                if (reader.HasRows)
                {
                    reader.Read();
                    date = reader.GetDateTime(0);

                }
                reader.Close();
            }

            var lastmonth = DateTime.Today.AddMonths(-6);

            if (lastmonth < date)
            {
                return new ValidationResult(false,"");
            }
            else
            {
                return new ValidationResult(true, null);
            }


        }
        catch
        {
            MessageBox.Show("Fehler");
        }
    }
    return new ValidationResult(true, null);
}

XAML绑定：

<Binding Path="TopArtikel" ValidatesOnExceptions="True"
        UpdateSourceTrigger="PropertyChanged">
    <Binding.ValidationRules>
        <local:MonthValidation/>
    </Binding.ValidationRules>
</Binding>

问题：TextBox占位符（WaterMarkLabel）不消失，输入内容与占位符重叠，边框未变色。

TextBox Style代码 #

<Style x:Key="txtStyle" TargetType="{x:Type TextBox}">
    <Setter Property="Background" Value="{DynamicResource {x:Static SystemColors.WindowBrushKey}}"/>
    <Setter Property="FontSize" Value="12"/>
    <Setter Property="BorderBrush" Value="#e5e7ea"/>
    <Setter Property="TextWrapping" Value="Wrap"/>
    <Setter Property="HorizontalAlignment" Value="Stretch"/>
    <Setter Property="KeyboardNavigation.TabNavigation" Value="None"/>
    <Setter Property="HorizontalContentAlignment" Value="Left"/>
    <Setter Property="BorderThickness" Value="2"/>
    <Setter Property="FocusVisualStyle" Value="{x:Null}"/>
    <Setter Property="AllowDrop" Value="true"/>
    <Setter Property="ScrollViewer.PanningMode" Value="VerticalFirst"/>
    <Setter Property="Stylus.IsFlicksEnabled" Value="False"/>

    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type TextBox}">
                <Grid>
                    <Border x:Name="border" Grid.ColumnSpan="2" Margin="0 2 0 2 " Background="{Binding Background, RelativeSource={RelativeSource AncestorType={x:Type TextBox}}}" 
                            CornerRadius="5" BorderThickness="1.5" BorderBrush="{Binding BorderBrush, RelativeSource={RelativeSource AncestorType={x:Type TextBox}}}"/>
                    <ScrollViewer Grid.Column="2" x:Name="PART_ContentHost" Margin="5,5,0,5" VerticalAlignment="Center" />
                    <Label Margin="5,0 0,0" HorizontalAlignment="Left" Grid.Column="1" x:Name="WaterMarkLabel" VerticalAlignment="Center"
                   Visibility="Collapsed" Foreground="Gray" FontFamily="Arial" Content="{Binding Tag, RelativeSource={RelativeSource AncestorType={x:Type TextBox}}}"/>
                </Grid>
                <ControlTemplate.Triggers>
                    <MultiTrigger>
                        <MultiTrigger.Conditions>
                            <Condition Property="Text" Value=""/>
                        </MultiTrigger.Conditions>
                        <Setter Property="Visibility" TargetName="WaterMarkLabel" Value="Visible"/>
                    </MultiTrigger>
                    <DataTrigger Binding="{Binding colorcheck}" Value="True">
                        <Setter Property="BorderBrush" Value="Red"/>
                    </DataTrigger>
                    <Trigger Property="IsFocused" Value="True">
                        <Setter Property="Background" Value="White"/>
                    </Trigger>
                    <Trigger Property="IsEnabled" Value="False">
                        <Setter Property="Foreground" Value="DimGray"/>
                    </Trigger>
                    <Trigger Property="IsReadOnly" Value="True">
                        <Setter Property="Background" Value="#f0f0f0"/>
                        <Setter Property="BorderThickness" Value="0"/>

                    </Trigger>
                    <EventTrigger 
                    RoutedEvent="TextBox.GotFocus">
                        <BeginStoryboard>
                            <Storyboard>
                                <ColorAnimation Storyboard.TargetName="border"    
                                Storyboard.TargetProperty="BorderBrush.Color"   
                                To="#5B7FFF" Duration="00:00:00.2" />
                            </Storyboard>
                        </BeginStoryboard>
                    </EventTrigger>
                    <EventTrigger 
                    RoutedEvent="TextBox.LostFocus">
                        <BeginStoryboard>
                            <Storyboard>
                                <ColorAnimation Storyboard.TargetName="border"    
                                Storyboard.TargetProperty="BorderBrush.Color"   
                                To="#e5e7ea" Duration="00:00:00.2" />
                            </Storyboard>
                        </BeginStoryboard>
                    </EventTrigger>

                </ControlTemplate.Triggers>
            </ControlTemplate>
        </Setter.Value>

    </Setter>
    <Style.Triggers>
        <MultiTrigger>
            <MultiTrigger.Conditions>
                <Condition Property="IsInactiveSelectionHighlightEnabled" Value="true"/>
                <Condition Property="IsSelectionActive" Value="false"/>
            </MultiTrigger.Conditions>
            <Setter Property="SelectionBrush" Value="{DynamicResource {x:Static SystemColors.InactiveSelectionHighlightBrushKey}}"/>
        </MultiTrigger>
    </Style.Triggers>
</Style>

求助 #

寻求正确的TextBox验证实现方式，使输入超过6个月的商品编号时边框正常变红且无UI异常。

内容的提问来源于stack exchange，提问作者NadiaBallshek