如果执行未完成，则阻塞计时器

Question

这是处理我的服务的类：

Imports System.Timers
Imports System.Configuration

Public Class Service
    Private _lastRun As DateTime = DateTime.Now
    Private ReadOnly log As log4net.ILog = log4net.LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType)

    Protected Overrides Sub OnStart(ByVal args() As String)
        log.Info("Service started.")

        Dim timer As New System.Timers.Timer(1 * 60 * 1000)
        AddHandler timer.Elapsed, AddressOf timer_Elapsed
        timer.Start()
    End Sub

    Private Sub timer_Elapsed(sender As Object, e As System.Timers.ElapsedEventArgs)
        Dim now As DateTime = DateTime.Now
        If now.Minute > _lastRun.Minute Then
            Dim m As New Main()
            m.Main()
            m = Nothing
        End If
        _lastRun = now
    End Sub

    Protected Overrides Sub OnStop()
        log.Info("Service is stopped")
    End Sub
End Class

一分钟后，Main 方法被执行。 Main 方法的运行时间是不可预测的。如果执行时间超过一分钟，则执行另一个 Main 方法。我会禁止这种行为，所以如果Main 方法仍在运行Main 方法的新实例，则必须禁止。我能做些什么？

Answer 1

定义你的计时器对象，使其在类中具有作用域：

private _timer As New System.Timers.Timer(1 * 60 * 1000)

然后当计时器结束时，禁用它直到你完成你的 Main 方法：

Private Sub timer_Elapsed(sender As Object, e As System.Timers.ElapsedEventArgs)
    _timer.Enabled = False
    Dim now As DateTime = DateTime.Now
    If now.Minute > _lastRun.Minute Then
        Dim m As New Main()
        m.Main()
        m = Nothing
    End If
    _lastRun = now
    _timer.Enabled = True
End Sub