您可以通过在DataTrigger中使用Text.Length来控制基于TextBox为空的控件的可见性：

<TextBox x:Name="txtSearch" />

<TextBlock Text="{Binding Text.Length, ElementName=txtSearch}">
    <TextBlock.Style>
        <Style TargetType="TextBlock">
            <Setter Property="Visibility"
                    Value="Visible" />
            <Style.Triggers>
                <DataTrigger Binding="{Binding Text.Length, ElementName=txtSearch}" Value="0">
                    <Setter Property="Visibility"
                            Value="Hidden" />
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </TextBlock.Style>
</TextBlock>

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您也可以为此创建一个自定义的EmptyToHidden转换器，它不需要样式：

public class EmptyToHidden : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value is string strValue &&
            !string.IsNullOrWhiteSpace(strValue))
        {
            return Visibility.Visible;
        }

        return Visibility.Hidden;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotSupportedException();
    }
}

型