vb.net - AccessViolationException 未处理？

Question

我正在处理一个目录项目，当程序没有被使用或空闲 3 分钟时，一个充当 的表单待机屏幕播放视频将显示(我使用 AxWindowsMediaPlayer )。通过单击表单中的任意位置，待机屏幕将关闭并返回主表单。

该程序运行良好，但有时在 关闭期间待机屏幕表单，应用程序崩溃并出现以下错误:

AccessViolationException was unhandled. Attempted to read or write protected memory. This is often an indication that other memory is corrupt.

这是完整的错误细节:

System.AccessViolationException was unhandled
  Message=Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
  Source=System.Windows.Forms
  StackTrace:
       at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.RunDialog(Form form)
       at System.Windows.Forms.Form.ShowDialog(IWin32Window owner)
       at System.Windows.Forms.Form.ShowDialog()
       at BuildingDirectory.main.tmrTime_Tick(Object sender, EventArgs e) in C:\Users\pc\Documents\Visual Studio 2010\Projects\testing\BuildingDirectory\BuildingDirectory\main.vb:line 128
       at System.Windows.Forms.Timer.OnTick(EventArgs e)
       at System.Windows.Forms.Timer.TimerNativeWindow.WndProc(Message& m)
       at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.Run(ApplicationContext context)
       at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.OnRun()
       at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.DoApplicationModel()
       at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.Run(String[] commandLine)
       at BuildingDirectory.My.MyApplication.Main(String[] Args) in 17d14f5c-a337-4978-8281-53493378c1071.vb:line 81
       at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
       at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()
  InnerException:

奇怪的是，错误指向的代码行包含在 try catch 中。阻止专门捕捉 AccessViolationException (之前是 exception，但还是遇到了问题):

Private Sub tmrTime_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles tmrTime.Tick
    Try
        lblTime.Text = TimeOfDay
        If standby = 2 Then
            standby += 1
            standByScreen.ShowDialog() ---> this is where the error is pointing to
        Else
            standby += 1
        End If
    Catch ex As AccessViolationException
        MessageBox.Show(ex.ToString)
    End Try
End Sub

请帮帮我，谢谢

Answer 1

这可能是由于standByScreen 变量的早期绑定(bind)。请注意，该错误是由 System.Windows.Forms 类引起的

尝试:

Dim stndByScreen As Object

stndByScreen = standByScreen
stndByScreen.ShowDialog()

而不是直接使用standByScreen