c# - .Net 类中的代码是否总是在创建它的线程上运行？

Question

在下面的示例代码中，timer elapsed 事件将始终在后台线程或主线程上运行吗？

Public Class MainClass    
    Dim SomeSubClassInstance As SomeSubClass

    Public Sub New()
        'Create a thread which will then create an instance of the sub class
        Dim T As New Threading.Thread(AddressOf CreateSomeSubClass)
        T.IsBackground = True
        T.Start()
    End Sub

    Private Sub CreateSomeSubClass()
        'This code runs on the background thread, and creates the instance of SomeSubClass
        SomeSubClassInstance = New SomeSubClass
    End Sub

    Public Class SomeSubClass
        Dim WithEvents tmrDoWork As Timers.Timer
        Public Sub New()
            tmrDoWork = New Timer
            tmrDoWork.Interval = TimeSpan.FromMinutes(1).TotalMilliseconds
            tmrDoWork.Start()
        End Sub

        Private Sub tmrDoWork_Elapsed(sender As Object, e As ElapsedEventArgs) Handles tmrDoWork.Elapsed
            'Will this code be run on the background thread that was created in the MainClass constructor?
        End Sub
    End Class
End Class

Answer 1

它也不会运行。它将在随机线程池线程上运行，除非您指定一个 SynchronizingObject 来将调用编码到另一个线程。

如果 SynchronizingObject 属性为 null，则在 ThreadPool 线程上引发 Elapsed 事件。如果 Elapsed 事件的处理持续时间长于 Interval，则该事件可能会在另一个 ThreadPool 线程上再次引发。在这种情况下，事件处理程序应该是可重入的。

https://msdn.microsoft.com/en-us/library/system.timers.timer(v=vs.110).aspx