使用绑定属性更新UserControl UI

Question

我有一个可以绑定到的属性的UserControl。此属性需要更新UserControl UI。UserControl有两个文本块，属性需要用字符串的一半更新一个文本块，用另一半更新另一个文本块。

UserControl 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>

UserControl CodeBehind (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是更新的，因为它使用了setter访问器，并执行了Parse()方法。但是，使用databind不能。

bAny反馈将不胜感激。

谢谢

Answer 1

Ryan Flohr的答案可以做你想做的事，但既然他提到了长缠绕法，我想我也会提出长缠绕法。长线法绝对是推荐的方法。

代码背后：

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项属性时，" get“和"Set”后面的代码实际上不会被调用。get'r和set'r只是"GetValue()“和"SetValue()”的包装器，便于代码隐藏使用。

我对您的问题的简短回答是，下面的代码更改至少可以使其以当前形式工作：

利用依赖项属性上的PropertyChangedCallback委托，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

，我对你问题的正确回答是：。

虽然这是合法的，但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，您应该有每个字符串的依赖项属性，然后将文本框绑定到它们。

我希望这能帮到你!

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。