Question [HELP] Threading issue

[Ztinel]

We have a stored procedure that executes in a long time so we decided to enclose it in a thread. Before executing the long stored procedure, the procedure should be locked so that only one user can execute the thread. However, I have noticed that a user can still execute twice. Here is the code.

Private Sub RunThread()
Dim ProcessThread As Thread = New Thread(AddressOf DoProcess)
DoProcess.Start()
...
End Sub
Private Shared lock as Object = New Object()
Private sub DoProcess
Try
Monitor.TryEnter(lock)
LockProcess() 'Inserts record in sp to denote that process is locked
Process() 'Long running Stored procedure
UnlockProcess() 'Updates newly inserted record in sp to unlock the process
...
Catch ex As Exception
Throw New Exception("Error: " + ex.Message)
Finally
Monitor.Exit(lock)
End Try
End Sub

The problem is when I tested the code by opening two browsers then simultaneously process, two records are being inserted into our lock table. The second user should not be able to process because the DoProcess is already locked. Can you help me what went wrong in my code. Thanks

 

[jmcilhinney]

Your Shared lock object is unique per AppDomain, so presumably each client is generating its own AppDomain.

 

[Ztinel]

Thanks for your reply, is there a way to share global variables in different browser or in different computers like storing the variable in the server?

 

[jmcilhinney]

I've never tried to communicate across AppDomains so I really couldn't tell you. That's the sort of terms you should be searching for. You can certainly store application variables and access them in each instance but I'm not sure how that relates to locking resources.