Question

首先，这是我在这个社区中的第一个问题。如果我做错了方法，请给我一些建议。

我需要一点帮助。我实际上是在BMEcat类库上工作，BMEcat是电子目录的数据交换格式。一切正常，但是我意识到处理非常大的文件时存在内存问题。因此，我想为任何已处理的商品/产品发送事件，而不是在内存中创建巨大的结构。这是我的问题开始的点。

我有一个类CTRANSACTION，从中派生了类CT_NEW_CATALOG，CT_UPDATE_PRODUCTS和CT_UPDATE_PRICES。

在基类CTRANSACTION中定义了一个事件：

Public Event Transaction_OnNewArticle(ByVal sender As Object, ByVal e As ArticleEventArgs)

类CBMECAT具有变量

Public WithEvents TRANSACTION As CTRANSACTION

和事件处理程序

Private Sub TRANSACTION_Transaction_OnNewArticle(sender As Object, e As ArticleEventArgs) Handles TRANSACTION.Transaction_OnNewArticle
    '...
End Sub

因为我无法从派生的Transaction_OnNewArticle类发送事件CT_NEW_CATALOG，所以我让它调用TransactionEventOnNewArticle中定义的CTRANSACTION方法。 TransactionEventOnNewArticle然后呼叫RaiseEvent Transaction_OnNewArticle。

一切正常，但事件Transaction_OnNewArticle并未触发。有办法解决吗？

Public MustInherit Class CTRANSACTION
    Inherits CBMECAT_NODE
    Public Event Transaction_OnNewArticle(ByVal sender As Object, ByVal e As ArticleEventArgs)
    Public Sub TransactionEventOnNewArticle(ByVal sender As Object,   ByVal e As ArticleEventArgs)
        RaiseEvent Transaction_OnNewArticle(sender, e)
    End Sub

Public Class CT_NEW_CATALOG
    Inherits CTRANSACTION

    Public Overrides Sub EventOnNewArticle(ByVal sender As Object, ByVal e As ArticleEventArgs)
        TransactionEventOnNewArticle(sender, e)
    End Sub

Public Class CBMECAT
    Inherits CBMECAT_NODE
    Public WithEvents TRANSACTION As CTRANSACTION  

    Private Sub TRANSACTION_Transaction_OnNewArticle(sender As Object, e As ArticleEventArgs) Handles TRANSACTION.Transaction_OnNewArticle
        'THIS method is never called - why?
    End Sub
End Class

更新

Public Class CBMECAT_ELEMENT 
    Public Overridable Sub EventOnNewArticle(ByVal sender As Object, ByVal e As ArticleEventArgs)
    End Sub 

'Please notice that CBMECAT_ELEMENT is the base class of EVERY other class in the library. 
'There is a class CBMECAT_NODE, which represents every node of the BMEcat XML structure and is derived from CBMECAT_ELEMENT. 
'In CBMECAT_NODE is EventOnNewArticle called whenever an article is processed;

Public Class CBMECAT_NODE
    Inherits CBMECAT_ELEMENT

    Public Overridable Function CreateChildNode(ByRef Nodename As String, Optional ByRef Parent As CBMECAT_NODE = Nothing) As CBMECAT_ELEMENT 
        Select Case Nodename
            [..] 
            Case ELEMENT_ARTICLE 
                CreateChildNode = New CARTICLE(Parent) 
                Dim e As New ArticleEventArgs With 
                { 
                    .ARTICLE = CreateChildNode 
                } 
                EventOnNewArticle(Me, e) 
                [..]

更新

Public Class CARTICLE
    Inherits CBMECAT_NODE
    Public Sub New(ByRef Father As CBMECAT_NODE)
    [..] 
    Public Overrides Sub Read()
    [..] 
    Public Overrides Sub Write()
    [..] 
    Public Overrides Sub Validate()
    [..]

更新

呼叫顺序：

CBMECAT_NODE.CreateChildNode调用CT_NEW_CATALOG.EventOnNewArticle <-确定

CT_NEW_CATALOG.EventOnNewArticle调用CTRANSACTION.TransactionEventOnNewArticle <-确定

CTRANSACTION.TransactionEventOnNewArticle触发事件Transaction_OnNewArticle 但事件处理者在CBMECAT中未收到该事件

如果我从CTRANSACTION中的方法手动触发事件，则事件被事件处理程序接收。

我还尝试了AddHandler / RemoveHandler，但这也行不通。

Answer 1

Visual Vincent，谢谢您帮助我解决问题。实际上，这有点“复杂”。

CBMECAT类具有以下读取方法：

Public Overrides Sub Read()
    MyBase.Read()
    GetContent(HEADER, ELEMENT_HEADER)
    Select Case TransactionType
        Case TransactionTypes.T_NEW_CATALOG
            GetContent(TRANSACTION, ELEMENT_T_NEW_CATALOG)
        Case TransactionTypes.T_UPDATE_PRICES
            GetContent(TRANSACTION, ELEMENT_T_UPDATE_PRICES)
        Case TransactionTypes.T_UPDATE_PRODUCTS
            GetContent(TRANSACTION, ELEMENT_T_UPDATE_PRODUCTS)
        Case Else
            ReportError(ERROR_BMECAT_UNKNOWN_TRANSACTION_TYPE)
    End Select
    Validate()
End Sub

MyBase.Read读取完整的XML文件，并且在读取时应触发事件。但是目前，变量 TRANSACTION 尚未通过其值分配。这是通过在读取过程完成后调用GetContent来完成的。

我已更改为：

TRANSACTION = New CT_NEW_CATALOG
TRANSACTION.Read()

现在所有事件均按预期触发。我将从 CBMECAT_ELEMENT 中删除 TransactionEventOnNewArticle（）。再次感谢Vincent，您的建议。：-）

不会触发继承的类事件

1 个答案: