Single Instance application crashes with an exeption...?

Single Instance application crashes with an exeption...?

• Pazu Choi

  Hi,

  Would you please post more details about the fatal exception you got That will help investigating this issue.

  Also, it's great if you can try this:
  - Click on 'View Application Events' button below the "Make single instance application" check box.
  - Add the following code:
  
  Private Sub MyApplication_StartupNextInstance(ByVal sender As Object, ByVal e As Microsoft.VisualBasic.ApplicationServices.StartupNextInstanceEventArgs) Handles Me.StartupNextInstance

  MsgBox("Second instance attempted")

  End Sub

  Private Sub MyApplication_UnhandledException(ByVal sender As Object, ByVal e As Microsoft.VisualBasic.ApplicationServices.UnhandledExceptionEventArgs) Handles Me.UnhandledException

  MsgBox(e.Exception.ToString)

  End Sub

  Try running your program again and see if you can get the full error message.

  Best regards,

  
  
  

• chrstdvd

  I have the same problem !!!
  
  I get the has encountered a problem and needs to close box , with a other msgbox uder that .
  Has someone worked how to stop it crashing and pass a command line to the second instance
  
  It sounds like it shouldn`t be very complex , but it is !!!!
  
  

• Jyoti Ranjan

  o.k.,. I’ve found my work around so I’ll say what happened and how I got around it for the other following in my foot steps.( Well the not crashing , which is a start )
  
  But before I do I’ve expend on my old problem and answer a couple of points.
  
  1/ handler code was in application.event from net doctor
  
  Private Sub MyApplication_StartupNextInstance(ByVal sender As Object, ByVal e as.vbMicrosoft.VisualBasic.ApplicationServices.StartupNextInstanceEventArgs) Handles Me.StartupNextInstance
  MsgBox("StartupNextInstance")
  End Sub
  I can`t tell you what the error was totally a win32 error, I think in nt.dll
  
  My work around is to make a starter module with :-
  
  Module Module1
  Public Sub main()
  Dim owned As Boolean
  Dim mut As New System.Threading.Mutex(True, "tryagain", owned)
  If owned Then
  MsgBox("Before")
  Application.Run(New Form1)
  MsgBox("Exit")
  mut.ReleaseMutex()
  Else
  MsgBox("repeat")
  End If
  End Sub
  End Module
  
  You have to switch off application framework to see the sub main !!!!
  
  Do you get a crach if you enable single instances on a blank form the second instance .
  
  
  

• mcfs

  Hi Huy,
  
  I've reviewed the detail in the links you have posted.
  
  However I am not using NOD32 AV software. I have also tried to do a clean boot of XP which would load the absolute minimum of services on startup and I still get the problem. One of the suggestions in the posts detailed above is to put a pause of 15 seconds into the application just before it terminates. This does improve matters although still doesn't resolve them as if you continually double click on the application icon it will crash after a few launches.
  
  I've included some C# code - but the problem is not with the source code but with something underlying environment - IE the .net framework, remoting, XP or hardware.
  
  I'm going to raise this as a support incident with Microsoft. Will post back here as and when I get progress on that front.
  
  
  Regards
  
  Peter
  
  
  SingleInstanceApplication.cs>>>>>>>>>>>>>
  using Microsoft.VisualBasic.ApplicationServices;
  
  namespace SingleInstanceSample
  {
  // SingleInstanceApplication.cs
  internal class SingleInstanceApplication : WindowsFormsApplicationBase
  {
  private static SingleInstanceApplication application;
  
  internal static SingleInstanceApplication Application
  {
  get
  {
  if (application == null)
  {
  application = new SingleInstanceApplication();
  }
  return application;
  }
  }
  
  // Must call base constructor to ensure correct initial
  // WindowsFormsApplicationBase configuration
  public SingleInstanceApplication()
  {
  // This ensures the underlying single-SDI framework is employed,
  // and OnStartupNextInstance is fired
  this.IsSingleInstance = true;
  }
  
  protected override void OnCreateMainForm()
  {
  this.MainForm = new MainForm();
  }
  }
  }
  
  Program.cs>>>>>>>>>>>>>>>>>>>>>>>>
  using System;
  using System.Windows.Forms;
  
  namespace SingleInstanceSample
  {
  internal static class Program
  {
  /// <summary>
  /// The main entry point for the application.
  /// </summary>
  [STAThread]
  private static void Main(string[] args)
  {
  Application.EnableVisualStyles();
  
  Application.SetCompatibleTextRenderingDefault(false);
  SingleInstanceApplication.Application.Run(args);
  }
  }
  }
  
  

• mrobichaud

  Hi,

  I found this feedback with the same call stack you got: http://connect.microsoft.com/feedback/ViewFeedback.aspx FeedbackID=93618&SiteID=210. The problem seems to be with NOD32 anti virus program (see http://connect.microsoft.com/feedback/Workaround.aspx FeedbackID=93618&SiteID=210). Would you please verify if it solves your issue

  You mentioned that you can reproduce the problem with C# code as well. If the issue persists, please simplify the C# code as much as you can to emphasize the issue and submit a feedback through https://connect.microsoft.com/site/sitehome.aspx SiteID=210. Based on the call stack I think this has more to do with remote call than our application framework code.

  Thank you for sharing great information, it really helps.

  Best regards,

  
  
  

• Harald Kjersen

  Thanks Huy for your reply.

  I've already contacted Panda about this problem and they are looking into it. I will send them your reply as well.

  I understand you can't fixed this, but yes, some improvement will be good. Now the application is just crashing and you don't know why. Take note that the same problem also occures with C# applications, so it's not only VB applications.

  Kind regards,
  Niels

  
  

• Rajiv Srinivasan-MSFT

  Hi Peter,

  Do you have the exception type Have you tried the steps suggested above to get the exception type

  If the steps above could not get the exception type, are you using remoting with TCP in your program The application framework uses TCP for communication between second instance and first instance. This may lead to exception as well.

  It would be great if you can share your code. Feel free to email me as well at Huy.Nguyen at microsoft.com.

  Best regards,

  
  
  

• Derwood

  I have had this crashing problem with single instance applications. Both in VB (using the code in the second part of this article: msdn.microsoft.com/msdnmag/issues/05/09/NETMatters) and in C# (using the code from chapter 14 of Chris Sells & Michael Weinhardt's excellent book on Forms 2.0 programming).
  
  I have trawled the net and also found that there are other who have similar problems - although it is not such a common problem that the web is littered with similar complaints. With Micahel Weinhardt's assistance we identified that the problem is not with the code, nor the .Net Framework directly but indirectly as a result of something to do with the machine. What the source of the problem is I do not yet know. If I take the compiled executables and move them to another machine they work fine and a single instance of the application runs.
  
  The problem remains and the mutex approach is a PARTIAL workaround which avoids the SingleInstance setting in VB or using the Microsoft.VisualBasic.Application code from a C# app. It is only a partial solution because you have no way of communicating with the existing running instance (EG to tell it to do something when a second instance loads). To add this functionality you then need to create a socket listner and communicate via sockets - however this also introduces security concerns and is the real reason to use the inbuilt single instance support in Microsoft.VisualBasic.Application because MS have done all the hard work on these aspects for you.
  
  If anyone can shed any light on what is causing this problem it would be very much appreciated. More details about it are:
  
  If you run the first instance from explorer then when you lauch a second instance you will get a GPF error indicating that memory is corrupt.
  
  If you do as above but step through the second instance in the VS debugger you will see that the second instance correctly identifies that an existing instance is running and the second instance will terminate normally. The error only occurs in the first instance but occurs as soon as the second instance terminates - no earlier, no later.
  
  If you run the first instance in the VS debugger and the second instance from Explorer then you can catch the 'unhandled' exception in Visual Studio - Actually you rely on VS to catch it because even if you put a try..catch wrapper around all your code in Main() it still doesn't catch the exception and VS reports it as an unhandled exception. The exception details are as follows:
  
  System.AccessViolationException was unhandled
  Message="Attempted to read or write protected memory. This is often an indication that other memory is corrupt."
  Source="System"
  StackTrace:
  at System.Net.UnsafeNclNativeMethods.OSSOCK.WSAGetOverlappedResult(SafeCl
  os eSocket socketHandle, IntPtr overlapped, UInt32& bytesTransferred,
  Boolean wait, IntPtr ignored)
  at System.Net.Sockets.BaseOverlappedAsyncResult.CompletionPortCallback(UI
  nt 32 errorCode, UInt32 numBytes, NativeOverlapped* nativeOverlapped)
  at System.Threading._IOCompletionCallback.PerformIOCompletionCallback(UIn
  t32 errorCode, UInt32 numBytes, NativeOverlapped* pOVERLAP)
  
  
  
  
  

• lindylars

  I also have this problem using Panda antivirus webclient. My application crashes after processing starting a second instance. I tried to exclude my application folder from scanning, but this doesn't solve the problem.
  
  I installed VS .NET 2005 SP1 Beta, but this made no difference. So I guess the problem is with Framework 2.0. Is there a hotfix available for this problem
  
  
  

• Qubic808

  Hi,

  I've received the report you opened on MS Connect as well.

  Enabling subsequent instances to contact the first instance of a single instance application requires remote communication using TCP/IP protocol. The first instance will listen on an available port of localhost. The second instance will obtain this port and try to contact the first instance. Panda antivirus is blocking remoting on your machine (see http://forums.microsoft.com/MSDN/ShowPost.aspx PostID=418569&SiteID=1).

  This will affect not only VB Single Instance application but also any programs that use .NET Framework remoting. Can you contact Panda for support as well

  AFAIK there is no hot fix for this. We may consider an improvement for VB Application Framework's Single Instance feature to let developer decide not to use remoting (hence subsequent instances will just exit).

  Best regards,

  
  
  

• Bayer

  I am havins similiar problems, I would like to create a single instance application in c# (2005) Attempting to migrate my old vb6 code (or rewrite in c#) I had used this code

  If Not App.PrevInstance Then

  Dim fLogin As New frmLogin
  fLogin.Show vbModal
  If Not fLogin.OK Then
  'Login Failed so exit app
  End
  End If
  Unload fLogin

  
  frmSplash.Show
  frmSplash.Refresh
  Set fMainForm = New frmMain
  Load fMainForm
  Unload frmSplash

  
  fMainForm.Show

  Else
  
  MsgBox "Sorry, " & Trim((App.Title)) & " is already running...", vbCritical
  End

  End If
  

  Can I use a similair construct in c# -- I noted that the vb.net allows this through application properties, alas c# does not.

  
  

• bighead

  Hi dDude,

  VB and C# does not contain support for App.PrevInstance by default. To write single instance application in C# you can follow chapter 14 of "Windows Forms 2.0 Programming" book. http://www.sellsbrothers.com/writing/wfbook/ has the chapter in PDF file.

  Best regards,

  
  
  

• RobGibbens

  hi, peter

  you can check this link, about vb comumication between instances of your program

  http://www.vbaccelerator.com/home/VB/Code/Libraries/Shell_Projects/Registering_File_Associations/article.asp

  hope this helps

  
  
  
• Single Instance application crashes with an exeption...?