使用绑定属性更新 UserControl UI

Question

我有一个带有可以绑定属性的 UserControl。此属性需要更新 UserControl UI。 UserControl 有两个文本块，属性需要用一半的字符串更新一个文本块，用另一半更新另一个文本块。

用户控件 XAML：

<UserControl x:Class="HexView"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         xmlns:local="clr-namespace:LearningWPF"
         mc:Ignorable="d" 
         d:DesignHeight="300" d:DesignWidth="300">
<Grid>
    <TextBlock x:Name="txtOne" Width="100" Height="100" HorizontalAlignment="Left" VerticalAlignment="Top" Margin="10,10,0,0">Hola</TextBlock>
    <TextBlock x:Name="txtTwo" Width="100" Height="100" HorizontalAlignment="Left" VerticalAlignment="Top" Margin="120,10,0,0">Adios</TextBlock>

</Grid>
</UserControl>

用户控制代码隐藏 (VB)

Imports System.ComponentModel

Public Class HexView

Private s_Rawstring As String

Public Sub New()

    ' This call is required by the designer.
    InitializeComponent()

    ' Add any initialization after the InitializeComponent() call.
End Sub

Public Shared ReadOnly RawStringProperty As DependencyProperty = DependencyProperty.Register("RawString", GetType(String), GetType(HexView))
Public Property Rawstring As String
    Get
        Return GetValue(RawStringProperty)
    End Get
    Set(value As String)
        SetValue(RawStringProperty, value)
        Parse()
    End Set
End Property

Private Sub Parse()
    txtOne.Text = Rawstring.Substring(0, Rawstring.Length / 2)
    txtTwo.Text = Rawstring.Substring(Rawstring.Length / 2)
End Sub
End Class

如果我将属性设置为

hexview.rawstring = "This is a sample property"

UserControlUI 已更新，因为它使用 setter 访问器并执行 Parse() 方法。但是使用数据绑定不会。

b任何反馈将不胜感激。

谢谢

Answer 1

Ryan Flohr's answer会做你想做的，但既然他提到了长篇大论的方法，我想我也会提出长篇大论的方法。啰嗦的方法绝对是推荐的方法。

后面的代码：

Imports System.ComponentModel

Public Class HexView

Private s_Rawstring As String

Public Sub New()

    ' This call is required by the designer.
    InitializeComponent()

    ' Add any initialization after the InitializeComponent() call.
End Sub

Public Shared ReadOnly RawStringProperty As DependencyProperty = DependencyProperty.Register("RawString", GetType(String), GetType(HexView), New PropertyMetadata(New PropertyChangedCallback(AddressOf RawStringPropertyChanged)))
Public Property Rawstring As String
    Get
        Return GetValue(RawStringProperty)
    End Get
    Set(value As String)
        SetValue(RawStringProperty, value)
    End Set
End Property

Private Shared Sub RawStringPropertyChanged(ByVal d As DependencyObject, ByVal e As DependencyPropertyChangedEventArgs)
    Dim control As HexView = CType(d, HexView)
    control.Parse()
End Sub

Public Shared ReadOnly ParsedStringOneProperty As DependencyProperty = DependencyProperty.Register("ParsedStringOne", GetType(String), GetType(HexView), New PropertyMetadata(String.Empty))
Public Property ParsedStringOne As String
    Get
        Return GetValue(ParsedStringOneProperty)
    End Get
    Set(value As String)
        SetValue(ParsedStringOneProperty, value)
    End Set
End Property

Public Shared ReadOnly ParsedStringTwoProperty As DependencyProperty = DependencyProperty.Register("ParsedStringTwo", GetType(String), GetType(HexView), New PropertyMetadata(String.Empty))
Public Property ParsedStringTwo As String
    Get
        Return GetValue(ParsedStringTwoProperty)
    End Get
    Set(value As String)
        SetValue(ParsedStringTwoProperty, value)
    End Set
End Property


Private Sub Parse()
    ParsedStringOne = Rawstring.Substring(0, Rawstring.Length / 2)
    ParsedStringTwo = Rawstring.Substring(Rawstring.Length / 2)
End Sub
End Class

XAML：

<UserControl x:Class="HexView"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         xmlns:local="clr-namespace:LearningWPF"
         mc:Ignorable="d" 
         d:DesignHeight="300" d:DesignWidth="300">
<Grid>
  <TextBlock x:Name="txtOne" Width="100" Height="100"
           HorizontalAlignment="Left" VerticalAlignment="Top" Margin="10,10,0,0"
           Text="{Binding RelativeSource={RelativeSource AncestorType={x:Type local:HexView}},Path=ParsedStringOne}"/>
    <TextBlock x:Name="txtTwo" Width="100" Height="100"
           HorizontalAlignment="Left" VerticalAlignment="Top" Margin="120,10,0,0"
           Text="{Binding RelativeSource={RelativeSource AncestorType={x:Type local:HexView}},Path=ParsedStringTwo}" />

</Grid>
</UserControl>

Answer 2

当您使用绑定访问依赖属性时，“Get”和“Set”背后的代码实际上并没有被调用。 get'r 和 set'r 只是“GetValue()”和“SetValue()”的一个包装器，方便代码隐藏使用。

我对您的问题的简短回答是以下代码更改，以至少使其以当前形式运行：

利用依赖属性上的 PropertyChangedCallback 委托并让它调用“Parse()”方法。

Public Shared ReadOnly RawStringProperty As DependencyProperty = DependencyProperty.Register("RawString", GetType(String), GetType(HexView), New PropertyMetadata(New PropertyChangedCallback(AddressOf RawStringPropertyChanged)))
Public Property Rawstring As String
    Get
        Return GetValue(RawStringProperty)
    End Get
    Set(value As String)
        SetValue(RawStringProperty, value)

    End Set
End Property

Private Shared Sub RawStringPropertyChanged(ByVal d As DependencyObject, ByVal e As DependencyPropertyChangedEventArgs)
    Dim control As HexView = CType(d, HexView)
    control.Parse()
End Sub

我对你的问题的正确回答有点啰嗦：

虽然这是合法的，但您通常应避免在代码隐藏中按名称引用控件。对于这两个字符串，您应该对每个字符串都有依赖属性，然后将文本框绑定到它们。

我希望这会有所帮助！

Answer 3

编写一个 IValueConverter ，它将为您完成工作。

class ParseStringConv : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            if (parameter.ToString() == "Left")
                return value.ToString().Substring(0, value.ToString().Length / 2);

            return value.ToString().Substring(value.ToString().Length / 2);
        }

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

用法：

<TextBlock Text="{Binding Name, Converter={StaticResource ParseConv}, ConverterParameter='Left'}" />

<TextBlock Text="{Binding Name, Converter={StaticResource ParseConv}, ConverterParameter='Right'}" />

传递适当的ConverterParameter。