Question

我想创建自定义文本框（它将包含简单的水印/提示文本），并且我遇到了依赖属性的问题。我的自定义类继承自TextBox类，包含两个文件（.xaml .cs） C＃代码文件非常简单：

public partial class HintTextBox : TextBox
{
    public string HintText
    {
        get { return (string)GetValue(HintTextProperty); }
        set { SetValue(HintTextProperty, value); }
    }
    public static readonly DependencyProperty HintTextProperty =
        DependencyProperty.Register(
            "HintText",
            typeof(string),
            typeof(HintTextBox),
            new FrameworkPropertyMetadata(string.Empty));
}

.xaml文件包含显示/隐藏水印的代码

<local:HintTextBox xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                xmlns:local="clr-namespace:Ribes.Client.GUI"
                xmlns:sys="clr-namespace:System;assembly=mscorlib">
<local:HintTextBox.Style>
    <Style TargetType="{x:Type local:HintTextBox}">
        <Style.Resources>
            <VisualBrush x:Key="CueBannerBrush" AlignmentX="Left" AlignmentY="Center" Stretch="None">
                <VisualBrush.Visual>
                    <Label Content="{Binding HintText, ElementName=local:HintTextBox}" Foreground="LightGray" />
                </VisualBrush.Visual>
            </VisualBrush>
        </Style.Resources>
        <Style.Triggers><!-- triggers changing content of control --></Style.Triggers>
    </Style>
</local:HintTextBox.Style>

我正在尝试简单地使用我的HintTextBox：

<local:HintTextBox HintText="hint text"></local:HintTextBox>

它不起作用。在线创建制动点后：

SetValue(HintTextProperty, value);

永远不会达到

代码。 TextBox的继承属性（Text，Background）工作正常：

<local:HintTextBox Text="example text" Background="Yellow"></local:HintTextBox>

我们可以在里面找到带有“示例文本”的正确黄色TextBox。

有人知道我的DP有什么问题吗？

Regars NQ

Answer 1

You will want to use Generic.xaml to style your textbox. To do this you will need to override the DefaultStyleKey in a static constructor.

HintTextBox.cs

public class HintTextBox : TextBox
{
    public static DependencyProperty HintTextProperty = DependencyProperty.Register("HintText", typeof(string), typeof(HintTextBox));

    public string HintText
    {
        get { return (string)GetValue(HintTextProperty); }
        set { SetValue(HintTextProperty, value); }
    }

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

Generic.xaml

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:Local="Ribes.Client.GUI">

    <!-- Describes how to style a HintTextBox -->
    <Style x:Key="{x:Type Local:HintTextBox}" BasedOn="{StaticResource {x:Type TextBox}}" TargetType="{x:Type Local:HintTextBox}">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type Local:HintTextBox}">
                    <Border x:Name="Border" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}"
                            BorderThickness="{TemplateBinding BorderThickness}" SnapsToDevicePixels="True">
                        <Grid x:Name="LayoutGrid">
                            <ScrollViewer x:Name="PART_ContentHost" Margin="2" />
                            <Label x:Name="HintText" Content="{Binding HintText, RelativeSource={RelativeSource TemplatedParent}}"
                                   FontStyle="Italic" Margin="2" Padding="2,0,0,0" />
                        </Grid>
                    </Border>
                    <ControlTemplate.Triggers>
                        <Trigger Property="HasText" Value="True">
                            <Setter Property="Visibility" TargetName="HintText" Value="Hidden" />
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</ResourceDictionary>

Answer 2

尝试这个并设置一个断点：

public string HintText
    {
        get { return (string)GetValue(HintTextProperty); }
        set { SetValue(HintTextProperty, value); }
    }
    public static readonly DependencyProperty HintTextProperty =
        DependencyProperty.Register(
            "HintText",
            typeof(string),
            typeof(HintTextBox),
            new FrameworkPropertyMetadata(null,FrameworkPropertyMetadataOptions.BindsTwoWayByDefault,(sender,e)=>{

                //Set Break Point Here

            });

Answer 3

我现在无法访问Visual Studio，但我认为您可能需要将FrameworkPropertyMetadata替换为UIPropertyMetadata到您的DependencyProperty中。

问题与依赖属性＆amp;自定义TextBox

3 个答案: