自定义控件未呈现

Question

下面的控件背后的想法是能够在没有任何文本时在文本框内显示标签。为此，我只使用了一个类似的工作控件，即 SearchTextBox，但有太多功能无法满足我的需要。

我怀疑下面样式的控制模板，但我没有发现它有任何明显的问题。不过，我很容易会错过一些对于有更多经验的人来说显而易见的东西。

我该如何修复或排除此问题？

干杯，
Berryl

代码

/// <summary>Light weight version of a <see cref="SearchTextBox"/></summary>
public class LabelTextBox : TextBox
{

    #region Dependency Properties

    #region Label Text

    /// <summary>Sets the 'watermark' text that acts as a label, identifying what this will search for.</summary>
    public static readonly DependencyProperty LabelTextProperty =
        DependencyProperty.Register("LabelText", 
            typeof (string), typeof (LabelTextBox), new PropertyMetadata("Search"));

    public string LabelText
    {
        get { return (string) GetValue(LabelTextProperty); }
        set { SetValue(LabelTextProperty, value); }
    }

    /// <summary>Brush for the label text.</summary>
    public static readonly DependencyProperty LabelTextColorProperty =
        DependencyProperty.Register("LabelTextColor", typeof (Brush), typeof (LabelTextBox));

    public Brush LabelTextColor
    {
        get { return (Brush)GetValue(LabelTextColorProperty); }
        set { SetValue(LabelTextColorProperty, value); }
    }

    #endregion

    #region Has Text

    private static readonly DependencyPropertyKey HasTextPropertyKey =
        DependencyProperty.RegisterReadOnly("HasText", 
            typeof (bool), typeof (LabelTextBox), new PropertyMetadata());

    /// <summary>True if the user has typed in text.</summary>
    public static readonly DependencyProperty HasTextProperty = HasTextPropertyKey.DependencyProperty;

    public bool HasText
    {
        get { return (bool)GetValue(HasTextProperty); }
        private set { SetValue(HasTextPropertyKey, value); }
    }

    #endregion

    #endregion

    #region Construction

    static LabelTextBox()
    {
        DefaultStyleKeyProperty.OverrideMetadata(typeof (LabelTextBox), new FrameworkPropertyMetadata(typeof (LabelTextBox)));
    }

    #endregion

    #region Event Handlers

    protected override void OnTextChanged(TextChangedEventArgs e)
    {
        base.OnTextChanged(e);

        HasText = Text.Length != 0;
    }

    #endregion

}

风格

<Style x:Key="{x:Type cc:LabelTextBox}" TargetType="{x:Type cc:LabelTextBox}">
    <Setter Property="Background" Value="{StaticResource SearchTextBox_Background}" />
    <Setter Property="BorderBrush" Value="{StaticResource SearchTextBox_Border}" />
    <Setter Property="Foreground" Value="{StaticResource SearchTextBox_Foreground}" />
    <Setter Property="BorderThickness" Value="1" />
    <Setter Property="SnapsToDevicePixels" Value="True" />
    <Setter Property="LabelText" Value="Search" />
    <Setter Property="FocusVisualStyle" Value="{x:Null}"/>
    <Setter Property="LabelTextColor" Value="{StaticResource SearchTextBox_LabelTextColor}" />

    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type cc:LabelTextBox}">

                <Border x:Name="Border" BorderBrush="{TemplateBinding BorderBrush}" Padding="2" 
                        BorderThickness="{TemplateBinding BorderThickness}"
                        Background="{TemplateBinding Background}"
                        >

                    <Grid x:Name="LayoutGrid">

                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="*" />
                            <ColumnDefinition Width="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=ActualHeight}" />
                        </Grid.ColumnDefinitions>

                        <ScrollViewer x:Name="PART_ContentHost" Grid.Column="0" />

                        <Label x:Name="LabelText" Grid.Column="0" 
                               Foreground="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=LabelTextColor}" 
                               Content="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=LabelText}" 
                               Padding="2,0,0,0" FontStyle="Italic" 
                               />

                    </Grid>

                </Border>

                <ControlTemplate.Triggers>

                    <!--input triggers (mouse over && keyboard focused-->
                    <Trigger Property="IsMouseOver" Value="True">
                        <Setter Property="BorderBrush" Value="{StaticResource SearchTextBox_BorderMouseOver}" />
                    </Trigger>
                    <Trigger Property="IsKeyboardFocusWithin" Value="True">
                        <Setter Property="BorderBrush" Value="{StaticResource SearchTextBox_BorderMouseOver}" />
                    </Trigger>

                    <!--Once the user has typed in search text-->

                    <Trigger Property="HasText" Value="True">
                        <!--Hide the label text-->
                        <Setter Property="Visibility" TargetName="LabelText" Value="Hidden" />
                    </Trigger>

                </ControlTemplate.Triggers>

            </ControlTemplate>
        </Setter.Value>

    </Setter>

    <!--
    Error display
    -->
    <Setter Property="Validation.ErrorTemplate">
        <Setter.Value>
            <ControlTemplate>
                <DockPanel LastChildFill="True">
                    <TextBlock DockPanel.Dock="Right" Text=" *" 
                               Foreground="Red" 
                               FontWeight="Bold" FontSize="16" 
                               ToolTip="{Binding ElementName=placeholder, Path=AdornedElement.(Validation.Errors).CurrentItem.ErrorContent}"/>
                    <Border BorderBrush="Red"  BorderThickness="1">
                        <AdornedElementPlaceholder Name="placeholder"></AdornedElementPlaceholder>
                    </Border>
                </DockPanel>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
    <Style.Triggers>
        <Trigger Property="Validation.HasError" Value="True">
            <Setter Property="Background" Value="LightYellow"/>
        </Trigger>
    </Style.Triggers>


</Style>

Answer 1

这似乎有效。我所做的只是将您的代码复制到一个名为 LabelTextBox 的类中，并将您的 Style 复制到 Themes< 的 Generic.xaml 资源字典中。 /code> 文件夹放置在项目根目录（我将画笔颜色更改为 LightBlue、LightGray、Blue 等）