vb.net - 如何在调用和事件 VB.net 时传递附加参数

Question

Public Event DocumentCompleted As WebBrowserDocumentCompletedEventHandler

Dim arg() As Object = {homeTeam, guestTeam}
        AddHandler browser.DocumentCompleted, New 
WebBrowserDocumentCompletedEventHandler(AddressOf DoStuff)

Private Sub DoStuff(ByVal sender As Object, ByVal e As WebBrowserDocumentCompletedEventArgs)

End Sub

在触发 DocumentCompleted 事件时如何传递 homeTeam 和 guestTeam。我想将上面的值放入 Dostuff 方法中。

请帮忙。

Answer 1

首先，你不能把它卡在不知名的地方:

Dim arg() As Object = {homeTeam, guestTeam}
AddHandler browser.DocumentCompleted,
           New WebBrowserDocumentCompletedEventHandler(AddressOf DoStuff)

AddHandler 可能需要位于某个 Initialize 方法中，该方法可能位于 Sub New 内，位于 InitializeComponent 之后，或在 Form_Load 内，或在您期望触发时(在特定事件之后)立即触发。请注意，此处您使用的是 native .NET 组件的默认事件和默认事件类型。在这种情况下，当触发时，您不能直接使用它已经提供的内容之外的任何内容。请参阅WebBrowser.DocumentCompleted Event on MSDN .

但是，您可以覆盖所有相关类并拥有自己的 MyWebBrowser 控件和自己的事件，其中将包含其他属性。请参阅下面的示例:

Public Class Form1
  Sub New()
    ' This call is required by the designer.
    InitializeComponent()

    Dim browser As New MyWebBrowser
    AddHandler browser.MyDocumentCompleted, AddressOf DoStuff
  End Sub

  Private Sub DoStuff(ByVal sender As Object, ByVal e As MyWebBrowserDocumentCompletedArgs)
    Dim guestTeam As String = e.GuestTeam 'guest team
    Dim homeTeam As String = e.HomeTeam 'and home team are both accessible
    'so you can do some processing on them
  End Sub

  Public Class MyWebBrowserDocumentCompletedArgs : Inherits WebBrowserDocumentCompletedEventArgs
    Dim _homeTeam As String
    Dim _guestTeam As String
    Public ReadOnly Property HomeTeam
      Get
        Return _homeTeam
      End Get
    End Property
    Public ReadOnly Property GuestTeam
      Get
        Return _guestTeam
      End Get
    End Property

    Sub New(url As Uri, homeTeam As String, guestTeam As String)
      MyBase.New(url)
      _homeTeam = homeTeam
      _guestTeam = guestTeam
    End Sub
  End Class

  Public Class MyWebBrowser : Inherits WebBrowser
    Public Delegate Sub MyWebBrowserDocumentCompletedEventHandler(e As MyWebBrowserDocumentCompletedArgs)
    Public Event MyDocumentCompleted As MyWebBrowserDocumentCompletedEventHandler

    Protected Overrides Sub OnDocumentCompleted(e As System.Windows.Forms.WebBrowserDocumentCompletedEventArgs)
      MyBase.OnDocumentCompleted(e)
      'homeTeam and guestTeam need to be extracted from the current instance of MyWebBrowser, and passed further
      RaiseEvent MyDocumentCompleted(New MyWebBrowserDocumentCompletedArgs(e.Url, "homeTeam", "guestTeam"))
    End Sub
  End Class
End Class

如果您的项目相对较小，您确实可以将它们作为全局变量，正如 @Vlad 在评论中建议的那样。