Question

我有一个VB.NET类Flasher，该类用于通过.Flash()方法刷新带有某些固件的设备。但是，在刷新过程中可能会发生错误，在这种情况下将触发事件。我无法弄清楚如何处理此事件并在.Flash()的调用堆栈中引发异常。

Class Flasher
    Private myDevice As New FlashLib.Device

    Public Function Flash() As String
        AddHandler myDevice.ErrorEvent, AddressOf OnError
        '... Do flashing stuff here that might send our `ErrorEvent` ...'
        myDevice.flash_firmware("myfirmware.fw")
        myDevice.restart()
        Threading.Thread.Sleep(5000)
        return "OK"
    End Function

    Public Sub OnError(ByRef Err As ErrEventArgs)
        errMsg = String.Format(
            "Device threw an error during flashing process. Type: {0}",
            Err.error)
        Throw New System.Exception(errMsg)
    End Sub

Flasher类依赖于C＃库FlashLib，它是ErrorEvent的发起者：

namespace FlashLib
{
    public delegate void ErrorEventHandler(ErrEventArgs err);

    public interface Device
    {
        event ErrorEventHandler ErrorEvent;
    }
}

问题是当我实例化Flasher并调用.Flash()时，想法是如果发生错误事件，.Flash()的调用者将被引发异常，但是在.Flash()执行的中间部分会跳出该函数并进入OnError()。我的catch子句不会在这里引发异常：

Dim flasher As New Flasher
Try
    flasher.Flash()
Catch
    Debug.Print("There was a problem with flashing")
End Try

相反，异常上升到顶部，并且显示错误消息框。然后从Flash()方法中中断的地方继续执行并继续进行。似乎VB.NET中的事件的行为就像软件中断一样：跳出您在处理程序中所做的任何操作，然后恢复之前的状态？我需要Flash()的调用方才能在触发ErrorEvent时捕获异常。

Answer 1

不是让您的OnError方法引发异常，而是让它设置一个可以在Flash中进行测试的标志，然后在发现异常的情况下引发该异常。例如

Class Flasher
    Private myDevice As New FlashLib.Device
    Private errMsg As String

    Public Function Flash() As String
        AddHandler myDevice.ErrorEvent, AddressOf OnError
        '... Do flashing stuff here that might send our `ErrorEvent` ...'

        If errMsg IsNot Nothing Then
            Throw New System.Exception(errMsg)
        End If

        myDevice.flash_firmware("myfirmware.fw")
        myDevice.restart()
        Threading.Thread.Sleep(5000)
        return "OK"
    End Function

    Public Sub OnError(ByRef Err As ErrEventArgs)
        errMsg = String.Format(
            "Device threw an error during flashing process. Type: {0}",
            Err.error)
    End Sub

触发事件时在函数调用中引发异常

1 个答案: