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prism - 简化的 PRISM 事件聚合器 - 订阅错误

问题描述

我在订阅 EventAggregator 时遇到困难，完整的 vb.net 代码如下。

'EventSystem' MODULE - 来自 Rachel 博客的简化 PRISM，转为 VB.net 模块，如下所示：

Imports Prism.Events

Module EventSystem

    Private _current As IEventAggregator

    Public ReadOnly Property Current As IEventAggregator
        Get

#Disable Warning BC40000 ' Type or member is obsolete
            Return If(_current, (CSharpImpl.__Assign(_current, New EventAggregator())))
#Enable Warning BC40000 ' Type or member is obsolete

        End Get
    End Property

    Private Function GetEvent(Of TEvent)() As PubSubEvent(Of TEvent)
        Return Current.GetEvent(Of PubSubEvent(Of TEvent))()
    End Function

    Sub Publish(Of TEvent)()
        Publish(Of TEvent)(Nothing)
    End Sub

    Sub Publish(Of TEvent)(ByVal [event] As TEvent)
        GetEvent(Of TEvent)().Publish([event])
    End Sub

    Function Subscribe(Of TEvent)(ByVal action As Action, ByVal Optional threadOption As ThreadOption = ThreadOption.PublisherThread, ByVal Optional keepSubscriberReferenceAlive As Boolean = False) As SubscriptionToken
        Return Subscribe(Of TEvent)(Sub(e) action(), threadOption, keepSubscriberReferenceAlive)
    End Function

    Function Subscribe(Of TEvent)(ByVal action As Action(Of TEvent), ByVal Optional threadOption As ThreadOption = ThreadOption.PublisherThread, ByVal Optional keepSubscriberReferenceAlive As Boolean = False, ByVal Optional filter As Predicate(Of TEvent) = Nothing) As SubscriptionToken
        Return GetEvent(Of TEvent)().Subscribe(action, threadOption, keepSubscriberReferenceAlive, filter)
    End Function

    Sub Unsubscribe(Of TEvent)(ByVal token As SubscriptionToken)
        GetEvent(Of TEvent)().Unsubscribe(token)
    End Sub

    Sub Unsubscribe(Of TEvent)(ByVal subscriber As Action(Of TEvent))
        GetEvent(Of TEvent)().Unsubscribe(subscriber)
    End Sub

    Private Class CSharpImpl
        <Obsolete("Please refactor calling code to use normal Visual Basic assignment")>
        Shared Function __Assign(Of T)(ByRef target As T, value As T) As T
            target = value
            Return value
        End Function
    End Class

End Module

我能够毫无问题地“发布”到“EventSystem”，代码如下，其中使用消息类“NewMessage”：

EventSystem.Publish(Of NewMessage)(New NewMessage With {.Msg = "Test"})

“订阅”的困难，代码如下，不幸的是不起作用：

EventSystem.Subscribe(Of NewMessage)(AppNavigate)

Private Sub AppNavigate(ByVal msg As NewMessage)
        MsgBox(msg.Msg)
End Sub

错误：未为 AppNavigate 的参数“msg”指定参数...这无法理解，类 NewMessage 具有属性 msg。如下

Public Class NewMessage
    Public Msg As String
End Class

请帮忙。谢谢

标签： prismsubscribeeventaggregator

解决方案

终于找到了 VB.NET 的解决方案，也许对某人有用。以上所有内容都可用于实现简化的 PRISM 事件聚合器，使用 lambda 表达式按如下方式执行“订阅”：

 EventSystem.Subscribe(Of NewMessage)(AppNavigate)

    Private ReadOnly AppNavigate As Action(Of NewMessage) = Sub(ByVal msg As NewMessage)
                                                                   MsgBox(msg.Msg) 
                                                            End Sub

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