vb.net - 没有可访问的“新”接受此数量的参数 - 错误

Question

我有这段代码

Dim _timer As System.Threading.Timer

Public Sub RunTimer2()
    _timer = New System.Threading.Timer(onSave(), 
                         Nothing, 
                         TimeSpan.FromSeconds(5),     
                         TimeSpan.FromSeconds(5))
End Sub

我得到错误重载解析失败，因为没有可访问的“新”接受这个数量的参数。对于我试图创建计时器的行。尽管我可以在 msdn 和库中的文档中看到它具有我使用的这 4 种可能的类型参数。我不明白...

Answer 1

您没有将委托传递给该onSave函数。您正在调用该onSave函数并将其返回值传递给Timer构造函数。您需要为函数创建委托并传递它，如下所示：

Dim _timer As System.Threading.Timer

Public Sub RunTimer2()
    _timer = New System.Threading.Timer(New TimerCallback(AddressOf onSave), 
                         Nothing, 
                         TimeSpan.FromSeconds(5),     
                         TimeSpan.FromSeconds(5))
End Sub

或者，如果您这样做，VB 会自动为您找出委托类型：

Dim _timer As System.Threading.Timer

Public Sub RunTimer2()
    _timer = New System.Threading.Timer(AddressOf onSave, 
                         Nothing, 
                         TimeSpan.FromSeconds(5),     
                         TimeSpan.FromSeconds(5))
End Sub

Answer 2

要在 vb.net 中声明一个计时器，您可以：

  Private MyTimer As System.Threading.Timer

  MyTimer = New System.Threading.Timer(AddressOf MyTimer_Tick, Nothing, RunEveryNMinutes * 60000, RunEveryNMinutes * 60000)

Private Sub MyTimer_Tick(ByVal state As Object)
    WriteEventLog("Timertick")

End Sub

Answer 3

5秒后启动计时器，每5秒调用一次

Private timer As System.Threading.Timer = New System.Threading.Timer(AddressOf DoWhatever, Nothing, New TimeSpan(0, 0, 5, 0), New TimeSpan(0, 0, 5, 0))

Private Sub dowhatever(sender As Object, e As Timers.ElapsedEventArgs)
   ' Do stuff
End Sub