Ensure that only on app instance is running per user ts session

[Xenio]

Hi,

I'd like to make sure that only one instance of my app is running per User
Session. In addition this has to work with user rights and in a Windows
2k/2k3 and Citrix Terminalserver environment.

The code I'm using prevents the app from creating a second instance on a TS.

What do I have to change?

Dim handler As ThreadExceptionHandler = New ThreadExceptionHandler
AddHandler Application.ThreadException, AddressOf
handler.Application_ThreadException

Dim findProcesses(), thisProcess As Process

thisProcess = Process.GetCurrentProcess()

findProcesses = Process.GetProcessesByName(thisProcess.ProcessName)
If findProcesses.Length = 1 Then
Dim aForm As New myForm
Application.Run(aForm)
End If

Thanks in advance for any hint

Xenio

 

[Ken Tucker [MVP]]

Hi,

Use a mutex instead

http://www.vb-tips.com/default.aspx?ID=59135549-e5dd-4501-9526-343ac05a7617

Ken

 

[Guest]

Check the PrevInstance property of the App Object to find out if any more
instance of your application is running, this works in VB6 but in fact I
don't know if the App object is still in VB.net.

 

[m.posseth]

Check the PrevInstance property of the App Object to find out if any more
instance of your application is running, this works in VB6 but in fact I
don't know if the App object is still in VB.net.

well it isn`t ( so you crashed and burned )

so the TS used the correct .Net 2003 substitute (
"Process.GetProcessesByName(thisProcess.ProcessName)")

however i guess this will fail in a Terminal server / Citrix context as
there the TS wants to have the ability to start multiple instances however
all in a seperate user context ( if i understood the question correct )

regards

Michel Posseth

 

[m.posseth]

Are you sure ???

I do not believe that a mutex is a solution in this case

Afaik the proggy will still see multiple instances in this case , as the
TS wants to have the ability to start multiple instances of his / her app
however they must then be running on a different user account in Terminal
server / Citrix


I guess that the only solution i see so far in this situation , is to create
your own ticket system


Or i am completely missing something here ( could be ) that a mutex will
only be vissible in the current users context , however in this situation it
would not be usable for a server app ( so i don`t think so ) .

I guess this could become a interesting topic......

regards

Michel Posseth [MCP]

 

[m.posseth]

FindWindow will return a valid handle if it finds the window class in the
current active session (desktop).
While using a mutex will prevent the user to start an application allready
running in another session.

yeahh i know using FindWindow is bad .... but euhh does anyone has a better
suggestion , to detect if someone trys to s art multiple instances of an app
in a users context ??

so a app might be started multiple times , however then under different user
accounts ( like on TS systems )


regards

Michel Posseth [MCP]

Are you sure ???

I do not believe that a mutex is a solution in this case

Afaik the proggy will still see multiple instances in this case , as the
TS wants to have the ability to start multiple instances of his / her app
however they must then be running on a different user account in Terminal
server / Citrix


I guess that the only solution i see so far in this situation , is to
create your own ticket system


Or i am completely missing something here ( could be ) that a mutex will
only be vissible in the current users context , however in this situation
it would not be usable for a server app ( so i don`t think so ) .

I guess this could become a interesting topic......

regards

Michel Posseth [MCP]

Hi,

Use a mutex instead

http://www.vb-tips.com/default.aspx?ID=59135549-e5dd-4501-9526-343ac05a7617

Ken

 

[m.posseth]

well i have been playing with that mutex thingy

and this seems to be the solution, for your Terminal server problem

call it on start of your application with usercontex = true to support
multiple instances that run on a different user contex
call it on start of your application with usercontex = false to support only
one instance
Imports System.Threading

Private oMutex As Mutex

Private Function InstanceRunning(ByVal UserContex As Boolean) As Boolean

Dim progid As String = "{4C91B499-109B-42c8-B68E-E125F321EED6}" ' change the
id for every app you deploy ( tools ,create guid )

oMutex = New Mutex(False, String.Concat(progid, CStr(IIf(UserContex,
System.Environment.UserName, ""))))

If oMutex.WaitOne(0, False) = False Then

oMutex.Close()

Return True

End

End If


End Function





am i the only one who found this a verry interesting topic / task



regards



Michel Posseth [MCP]