c# - 另一个类中的 WPF 事件处理程序

Question

我为一些自定义 WPF 控件构建了一系列事件处理程序。事件句柄根据包含的数据类型(电话号码、邮政编码、货币值(value)等)格式化用户输入或离开文本框时显示的文本。

现在，我在直接附加到 xaml 的 C# 代码中本地拥有所有事件。因为我开发了一个 could 控件，这意味着逻辑重复了很多，如果我想更改程序范围的功能，我将不得不在事件代码所在的所有位置进行更改。

我确信有一种方法可以将我所有的事件处理程序放在一个类中。谁能帮我指出正确的方向？

我看到这篇文章:Event Handler located in different class than MainWindow但我不确定它是否与我正在做的事情直接相关。我宁愿对我现有的逻辑做一些小改动，因为它可以工作，然后将所有内容重写为命令。

如果可能的话，我基本上想要这样的东西:

LostFocus="ExpandedTextBoxEvents.TextBox_LostFocus"

做这样的事情很容易:

private void TextBoxCurrencyGotFocus(object sender, RoutedEventArgs e)
{
    ExpandedTextBoxEvents.TextBoxCurrencyGotFocus(sender, e);
}
private void TextBoxCurrencyLostFocus(object sender, RoutedEventArgs e)
{
    ExpandedTextBoxEvents.TextBoxCurrencyLostFocus(sender, e);
}

但这不太优雅。

Answer 1

Attached Properties是你想要的一种方法。我经常使用它们。

附加属性代码:

Public Class TextBoxFormatter

    ' ------------------------------------------------------
    ' Define the FormatType attached property

    Public Shared ReadOnly FormatTypeProperty As DependencyProperty = _
        DependencyProperty.RegisterAttached( _
            name:="FormatType", _
            propertyType:=GetType(TextBoxFormatterType), _
            ownerType:=GetType(TextBoxFormatter), _
            defaultMetadata:=New FrameworkPropertyMetadata( _
                defaultValue:=TextBoxFormatterType.None, _
                PropertyChangedCallback:=New PropertyChangedCallback(AddressOf FormatTypePropertyChanged) _
            ) _
        )
    ' ------------------------------------------------------
    ' Define the "getter" and "setter" for FormatType
    Public Shared Function GetFormatType(ByVal target As DependencyObject) As TextBoxFormatterType
        target.GetValue(FormatTypeProperty)
    End Function
    Public Shared Sub SetFormatType(ByVal target As DependencyObject, ByVal value As TextBoxFormatterType)
        target.SetValue(FormatTypeProperty, value)
    End Sub

    ' ------------------------------------------------------
    ' Define the FormatType "PropertyChanged" event handler

    Private Shared Sub FormatTypePropertyChanged(ByVal target As DependencyObject, ByVal e As DependencyPropertyChangedEventArgs)
        If CType(e.NewValue, TextBoxFormatterType) = TextBoxFormatterType.None Then
            UnregisterFormatTypeControl(target)
        Else
            RegisterFormatTypeControl(target)
        End If
    End Sub

    ' ------------------------------------------------------
    ' Define the a collection of event listerns for the
    ' FormatType "PropertyChanged" event

    Private Shared _registeredFormatTypeControlDelegates As New Dictionary(Of TextBox, RoutedEventHandler)

    ' ------------------------------------------------------
    ' Register a control as an event listener
    ' (also, attach to the control's LostFocus event)

    Private Shared Sub RegisterFormatTypeControl(ByVal candidate As DependencyObject)
        Dim l_control = TryCast(candidate, TextBox)
        If l_control IsNot Nothing Then
            Dim l_handler = New RoutedEventHandler(AddressOf FormatTypeControl_LostFocus)
            _registeredFormatTypeControlDelegates.Add(l_control, l_handler)
            l_control.AddHandler(TextBox.LostFocusEvent, l_handler)
        End If
    End Sub

    ' ------------------------------------------------------
    ' Unregister a control as an event listener
    ' (also, unattach from the control's LostFocus event)

    Private Shared Sub UnregisterFormatTypeControl(ByVal candidate As DependencyObject)
        Dim l_control = TryCast(candidate, TextBox)
        If l_control IsNot Nothing AndAlso _registeredFormatTypeControlDelegates.ContainsKey(l_control) Then
            Dim l_handler = _registeredFormatTypeControlDelegates(l_control)
            l_control.RemoveHandler(TextBox.LostFocusEvent, l_handler)
            _registeredFormatTypeControlDelegates.Remove(l_control)
        End If
    End Sub

    ' ------------------------------------------------------
    ' On the control's LostFocus event, apply the format
    ' (You could apply the format based on another event,
    ' just be careful if using the TextChanged event - it
    ' will fire whether the user has changed the text or
    ' your code has changed the text - could introduce an
    ' infinite loop)

    Private Shared Sub FormatTypeControl_LostFocus(ByVal sender As Object, ByVal e As RoutedEventArgs)
        Dim l_textBox = TryCast(e.Source, TextBox)
        If l_textBox IsNot Nothing Then

            Dim l_formatType = CType(l_textBox.GetValue(FormatTypeProperty), TextBoxFormatterType)
            Select Case l_formatType

                Case TextBoxFormatterType.SocialSecurityNumber
                    ' Apply the format to the l_textBox
                    ' (What do you want a social security number to look like?)

                Case TextBoxFormatterType.ZipCode
                    ' Apply the format to the l_textBox
                    ' (What do you want a zip code to look like?)

                Case TextBoxFormatterType.Etc
                    ' Apply the format to the l_textBox

            End Select

        End If
    End Sub

End Class

Public Enum TextBoxFormatterType
    None
    ZipCode
    SocialSecurityNumber
    Etc
End Enum

上面看起来有点乱，但是一旦代码写好了(一次)，你可以在你的 UI 中反复使用它:

<Window x:Class="Window1"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:this="clr-namespace:WpfApplication1"
        Title="Window1">
  <Grid>

    <StackPanel>

      <TextBox this:TextBoxFormatter.FormatType="SocialSecurityNumber" />
      <TextBox this:TextBoxFormatter.FormatType="ZipCode" />
      <TextBox this:TextBoxFormatter.FormatType="None" />

    </StackPanel>

  </Grid>
</Window>

这种方法的一个优点是“FormatType”成为一个依赖属性，这意味着您可以在运行时将值绑定(bind)到它(而不是像上面的示例那样只是硬编码)。例如:

<TextBox this:TextBoxFormatter.FormatType="{Binding ViewModel.DesiredFormat}" />