Question

我正在使用与RFID终端一起使用的API。当任何终端触发事件时，API会处理它并将适当的参数传递给过程：

For i = 0 to NumberOfTerminals - 1
    myTerminals(i).ID = i
    myTerminals(i).API.Connect()
    AddHandler myTerminals(i).API.OnRFID, AddressOf OnRFIDSub
End For

Private Sub OnConnectSub(ByVal RFID As String, ByVal EventTime As String)
    MsgBox(RFID & " : " & EventTime)
End Sub

问题是，当触发事件时，API没有传递sender或e属性。有没有办法知道哪个终端在没有sender对象的情况下触发了事件？

提前感谢。

Answer 1

扩展nvoigts回答

For i = 0 to NumberOfTerminals - 1
    myTerminals(i).ID = i
    myTerminals(i).API.Connect()
    'copy the id as there are problems with closing over iteration variables.
    dim id as integer = i
    'Lamda sub to close over id
    AddHandler myTerminals(i).API.OnRFID, _
        Sub(ByVal RFID As String, ByVal EventTime As String) _ 
            OnRFIDSub(RFID,EventTime,id) 
End For

Private Sub OnConnectSub(ByVal RFID As String, ByVal EventTime As String, 
                         ByVal Sender as Integer) 'Sender now contains the terminal ID
    MsgBox(RFID & " : " & EventTime)
End Sub

Answer 2

vb语法让我感到厌烦，但似乎你可以为每个终端添加一个不同的处理程序。因此，向终端i添加一个处理程序，将其终端（i）传递给作为发送方的函数。

实现这一目标的最简单方法可能是lambda表达式。

查找发件人而不将其作为.NET中的参数传递

2 个答案: