Silverlight - 回车键触发默认按钮

@L_696_0@常见的需求是，用户在某个TextBox中输入回车键，自动触发界面上的某个按钮。比如登录窗口中，用户输入完密码后按回车，自动触发登录按钮。@H_403_7@

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Silverlight (4.0)目前还没有像winform程序那样可通过设置@L_696_0@属性值来简单实现。@H_403_7@

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Patrick Cauldweel 提供了@L_696_0@方案， Kyle Burns 做了些改进，@L_674_20@了通用性，并解决了前者的一些缺点。@H_403_7@

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受Kyle启发，我的实现方法是实现为@L_696_0@Panel (Grid,Canvas,StackPanel的基类)控件的Behavior。该实现需要引用System.Windows.Interactivity.dll@H_403_7@

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@L_696_0@示例登录窗口的Xaml如下：@H_403_7@

<StackPanel>@H_403_7@

<i:Interaction.behaviors>@H_403_7@

<command:DefaultButtonBehavior DefaultButtonName="{Binding ELEMENTNAME=btnLogin, Path=Name}" />@H_403_7@

</i:Interaction.behaviors>@H_403_7@

<TextBox Text="{Binding LoginNamE}"/>@H_403_7@

        <passwordBox password="{Binding LoginpassworD}"/>@H_403_7@

<Button Content="Login" x:Name="btnLogin" Command="{Binding LoginCommanD}"/>@H_403_7@

</StackPanel>@H_403_7@

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DefaultButtonBehavior类(vb.net):@H_403_7@

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Imports System.Windows.Interactivity
Imports System.Windows.Data
Imports System.Windows.Automation.Peers
Imports System.Windows.Automation.Provider
Imports System.Linq
 
Namespace Commands
 
    Public Class DefaultButtonBehavior
        Inherits Behavior(Of Panel)
 
        Public Property DefaultButtonName As String
            Get
                Return CType(GetValue(DefaultButtonNameProperty), String)
            End Get
            Set(ByVal value As String)
                SETVALue(DefaultButtonNameProperty, value)
            End Set
        End Property
 
        Public Shared ReadOnly DefaultButtonNameProperty As DependencyProperty _
        = DependencyProperty.Register(name:="DefaultButtonName", _
        propertyType:=GetType(String), _
        ownerType:=GetType(DefaultButtonBehavior), _
        typeMetadata:=Nothing)
 
        Protected Overrides Sub OnAttached()
            @H_988_37@myBase.onAttached()
            AddHandler AssociatedObject.KeyUp, AddressOf AssociatedObject_KeyUp
        End Sub
 
        Protected Overrides Sub OnDetaching()
            @H_988_37@myBase.onDetaching()
            RemoveHandler AssociatedObject.KeyUp, AddressOf AssociatedObject_KeyUp
        End Sub
 
        Private Sub AssociatedObject_KeyUp(ByVal sender As Object, ByVal e As KeyEventArgs)
            If e.Key = Key.Enter Then
 
                Dim defaultButton As Button = AssociatedObject.Children.ofType(Of Button).FirstOrDefault(Function(X) x.Name = DefaultButtonName)
                If defaultButton Isnot Nothing And defaultButton.IsEnabled Then
 
                    'update binding source of textBox
                    Dim inputTxts = AssociatedObject.Children.ofType(Of TextBox)()
                    For Each txt In inputTxts
                        Dim exp As BindingExpression = txt.GetBindingExpression(TextBox.TextProperty)
                        exp.updatesource()
                    Next
 
                    'update binding source of password
                    Dim inputPwds = AssociatedObject.Children.ofType(Of passwordBox)()
                    For Each pwd In inputPwds
                        Dim exp As BindingExpression = pwd.GetBindingExpression(passwordBox.passwordProperty)
                        exp.updatesource()
                    Next
 
                    Dim peer As New ButtonAutomationPeer(defaultButton)
                    Dim invoke As IInvokeProvider = peer.GetPattern(PatternInterface.InvokE)
                    invoke.Invoke()
                    e.Handled = True
                End If
               
            End If
        End Sub
 
    End Class
 
End Namespace