Single instance of Pocket PC Console application!

Hello,
Would anyone happen to know how to force a single instance of a Console application on a Pocket PC (IPAQ) using vb.net (Visual Studio 2008)? I have been bouncing my head off the wall on this one. I just can't seem to grasp it! I have tried the mutex way but it does not seem to be working. Below is the code I have been trying to get to work.

Code:

---

'This is the Class
Imports System
Imports System.Runtime.InteropServices
Imports System.Reflection

Public Class OneInstance

    Private Const ERROR_ALREADY_EXISTS As Integer = 183

    <DllImport("CoreDll.Dll")> Private Shared Function GetLastError() As Integer
    End Function
    <DllImport("CoreDll.Dll", EntryPoint:="CreateMutexW")> Private Shared Function CreateMutex(ByVal lpMutexAttributes As IntPtr, ByVal InitialOwner As Boolean, ByVal MutexName As String) As Integer
    End Function

    Public Function IsInstanceRunning() As Boolean
        Dim applicationname As String = System.Reflection.Assembly.GetExecutingAssembly().GetName().Name()
        If CreateMutex(IntPtr.Zero, True, applicationname) <> 0 Then
            Return Marshal.GetLastWin32Error() = ERROR_ALREADY_EXISTS
        Else
        End If
        Return False
    End Function
End Class

---

Code:

---

'This is how I am calling it inside of the module
Imports System
Imports System.Xml
Imports System.Diagnostics

Module Module1
    Sub Main()
        On Error Resume Next
Dim a As New OneInstance
        If a.IsInstanceRunning() Then
'End the second, third, etc process           
Process.GetCurrentProcess().Dispose()
        End If
          ' Continue on with the rest of the code
      End Sub
End Module

---

Any comments and or help is appreciated!:)
Thanks,
Jlynn001

If this is pocketpc then the operating system ensures on your behalf that there is only one instance of the application running.

There is a discussion on this in the last few weeks, if you search the forums

Well that is the confusing part as it is considered pocketpc but the OS is WinCE. So it in itself does not limit an application to only one instance of itself.

Windows CE doesn't disallow multiple instances - Pocket PC DOES disallow multiple instances.

PocketPC runs on top of Windows CE

I don't know if console apps are treated differently though :(

If so, the createmutex should sort it. I posted working code for this in an earlier thread.

Hi Pete,
Sorry I must be doing something wrong. I just can't get it to work. I copied your code and it still is not working can you possibly tell me what I am doing wrong? No matter what I try it just keeps allowing more then one instance. The application name is PDA411a.exe. The code is below that I have been trying to use.

Code:

---

Imports System
Imports System.Xml
Imports System.Diagnostics
Imports System.Runtime.InteropServices
Imports System.Reflection

Module Module1
    Sub Main()
        Dim p As New System.Diagnostics.Process()       
        On Error Resume Next
        Call CreateMutex(CInt(0), 1, "<PDA411a")
        If GetLastError() = ERROR_ALREADY_EXISTS Then
          MsgBox("One is running already")
        Else
        End If
        MsgBox("Waiting to run part B")
        p.StartInfo.FileName = "PDA411b.exe"
        p.Start()
  End Sub
       
    Public Declare Function CreateMutex Lib "Coredll.dll" (ByRef lpMutexAttributes As Integer, ByVal bInitiaOwner As Integer, ByVal lpName As String) As Integer
    Public Declare Function GetLastError Lib "CoreDll.dll" () As Integer
    Const ERROR_ALREADY_EXISTS = 183
End Module

---

You tried stepping through the code?

Hi,
if you are using Sub Main, then the program will drop through and end, so PDA411a won't exist, as it will have terminated.

You checked using TaskManager?

Hi,
I have not stepped through as I can't start the second instance in order to test it. I have checked with Task Manager and it is running. It shows as PDA411a.exe. I added the MsgBox ("Waiting to run part B") so it would wait during my testing.

If I take out the 'On Error Resume Next' (Shudder) - the application doesn't run - it fails when it gets to the messagebox.

Interesting. I just deployed it to the emulator. Ran it which stops and waits at the part B message box. Then debugged it on the emulator and it worked fine. Very interesting! I am assuming you are saying it bombs at the already running message box? If I change it to your application.Exit(). I get the Name application is not declared error. How would I declare it? Sorry I am very new at this and I just can't grasp it yet!

Even more interesting is that the same exe which works on the emulator does not work on the PDA itself. By working I mean stop or detect the second instance of the application.

If you take out the on resume next then it fails at the line...

MsgBox("Waiting to run part B")

Using SubMain you do not exit - when you application reaches the 'End Sub' of 'Sub Main' then it will automatically exit.

So as it stands, without the messageboxes, your application would start up, start up PDA411b and then end.

Here is all the code. Maybe it will help!

Code:

---

Imports System
Imports System.Xml
Imports System.Diagnostics
Imports System.Runtime.InteropServices
Imports System.Reflection

Module Module1
    Sub Main()
        On Error Resume Next
        Call CreateMutex(CInt(0), 1, "PDA411a")
        If GetLastError() = ERROR_ALREADY_EXISTS Then
            'Application.Exit()
            MsgBox("One is running already")
        Else
        End If
        Dim stra As String
        Dim s As String = ""
        Dim userid As String = ""
        Dim username As String = ""
        Dim usercred As String = ""
        Dim resid As String = ""
        Dim resname As String = ""
        Dim devtype As String = ""
        Dim p As New System.Diagnostics.Process()
        Dim MyValue As String = SearchValue("\?\?.ini", "DeviceName")
        Dim datafile As String
        If MyValue = "" Then
            MyValue = System.Net.Dns.GetHostName()
        Else
        End If
        Dim oWrite As System.IO.StreamWriter
        datafile = ("My Documents\Personal\" & MyValue & ".txt")
        oWrite = IO.File.AppendText(datafile)
        ' The xml node reader.
        Dim reader As XmlNodeReader = Nothing
        ' The xml document to read from.
        Dim doc As New XmlDocument()
        ' Load the xml document.
        doc.Load("My Documents\?\?.xml")
        ' Set the reader to open the xml document.
        reader = New XmlNodeReader(doc)
        ' Read all the data in the XML document and display it.
        'oWrite.WriteLine("Launched: " & Now)
        While reader.Read()
            Select Case reader.NodeType
                Case XmlNodeType.Element
                    ' Keep track of the element that the user is on.
                    s = reader.Name
                Case XmlNodeType.Text
                    If Not s.Equals("user_id") Then
                    Else
                        userid = reader.Value
                    End If
                    If Not s.Equals("user_name") Then
                    Else
                        username = reader.Value
                    End If
                    If Not s.Equals("user_credentials") Then
                    Else
                        usercred = reader.Value
                    End If
                    If Not s.Equals("resident_id") Then
                    Else
                        resid = reader.Value
                    End If
                    If Not s.Equals("resident_name") Then
                    Else
                        resname = reader.Value
                    End If
                    If Not s.Equals("device_type") Then
                    Else
                        devtype = reader.Value
                    End If
            End Select
        End While
        If Not (reader Is Nothing) Then
            reader.Close()
        End If
        stra = IO.File.GetLastWriteTime("\My Documents\?\?.xml")
        oWrite.WriteLine("Launched: " & Now & "," & userid & "," & username & "," & usercred & "," & resid & "," & resname & "," & devtype & "," & MyValue & "," & stra)
        oWrite.WriteLine()
        oWrite.Close()
        'Launch
        p.StartInfo.FileName = "\Program Files\?\?.exe"
        p.Start()
        'Wait for exit then Launch PDA411b.exe
        'MsgBox("Waiting to run part B")
        p.WaitForExit()
        p.StartInfo.FileName = "PDA411b.exe"
        p.Start()
    End Sub
    Private Function SearchValue(ByVal File As String, ByVal Value As String) As String
        Try
            Dim SzR As New System.IO.StreamReader(File)
            Dim MyString() As String
            While SzR.Peek <> -1
                MyString = Strings.Split(SzR.ReadLine, "=")
                If MyString(0) = Value Then
                    SzR.Close()
                    Return MyString(1)
                End If
            End While
            SzR.Close()
            Return ""
        Finally
        End Try
    End Function
    Public Declare Function CreateMutex Lib "Coredll.dll" (ByRef lpMutexAttributes As Integer, ByVal bInitiaOwner As Integer, ByVal lpName As String) As Integer
    Public Declare Function GetLastError Lib "CoreDll.dll" () As Integer
    Const ERROR_ALREADY_EXISTS = 183
End Module

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Ultimately I would like to replace the One is running already message box with the exit application command, but I can't get that to work either.

Just wanted to say thanks for the help also Pete. I do really appreciate it!

HI,
you really need to step through your code to see what is happening. Check the value of GetLastError - I think you will find it is non-zero.

Certainly remove the 'On Error Resume Next' which will hide a multitude of sins.

As I explained, using Sub Main will drop through and exit the application, so you need structure your code accordingly.

Hi Pete,
I did step through the code. It works on the emulator but not on the Ipaq itself. I don't understand why! When I run it. It goes right to the waiting for part B message box. Which is what it should do. If I run it again it goes to the One is already running message box. Which it is suppose to do. If I try the same thing on the device itself. It always goes to the waiting to run part B. No matter how many times I run it.

Have you checked the task manager on the device?
Did you step through the code on the device, as well as the emulator?

Yes that is the strange part. Everything is the same on both the emulator and IPAQ. Except the results of the code.

Hi Pete,
Quick update. It seems the emulator I was using was a PocketPC 2003 SE Emulator. The device is a iPAQ, and or a WinCE device. Now that I am using the Windows Mobile 6 Classic Emulator. It does not work properly either. It goes right to the Waiting to Run part B message box. So it has to be something with WinCE and the code correct?

If the device is an iPaq, it will be running Windows Mobile so shouldn't need a mutex - the operating system will take care of it.
Settings>system>About
Should show exactly what it is running.

That was what I thought as well but it does allow more than one instance to run. Maybe it is my coding not sure. I thought WM would block and force only one instance, but this does not seem to be the case. I see that GetLastError() always comes back with the error code of 6. Which is a invalid_handle_error I believe. So what would be causing that? Thanks for all your help Pete. I am really just learning this stuff and it is quite confusing!

I was able to get this working by adding a form to it. Once switched from console to a form application it is working as it should now! Thanks for all your help Pete!

Glad you got it sorted - Console apps obviously work differently :)

The device is a iPAQ, and or a WinCE device. Now that I am using the Windows Mobile 6 Classic Emulator.

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Quote:

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the device is a ipaq, and or a wince device. Now that i am using the windows mobile 6 classic emulator.

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?????

try this very simple to write

http://net-informations.com/vbprj/fr...e-instance.htm

thanks
Rob.