Threading Problem

[TriceD]

Greetings all,

I have some difficulties concerning threading and hope you guys could be of help.

Let's say I have the following class:

Public Class myClass
    
    Public Sub closeSomething()

    End Sub

    Public Sub doSomethingElse()
       
    End Sub

    Public Function doSomething() As String
          Dim ret As String = "Blablabla"
          Dim ThreadX As New System.Threading.Thread(AddressOf doSomethingElse)
          
          ThreadX.IsBackground = True
          ThreadX.Start()

          While ThreadX.ThreadState <> System.Threading.ThreadState.Aborted AndAlso ThreadX.ThreadState <> System.Threading.ThreadState.Stopped
                    System.Threading.Thread.Sleep(1)
          End While

          Return ret
    End Function

End Class

Let's say I use the above class in the following way:

1- Dim str As String
2- Dim x As New myClass
3- str = x.doSomething()
4- x.closeSomething()

I've included line numbers so I can just refer the lines by their numbers.
My problem is, when the program executes, line 4 seems to be executed earlier than I want it to. It gets executed while ThreadX is still running in line 3. How can I force the program to wait until ThreadX has finished executing, before it executes line 4?

[Ramy Mahrous]

That's normal because you don't stop the main thread, your process or application in line 3 has 2 threads working in parallel..

[TriceD]

Thanks for your reply RamyMahrous, but how do I stop the main thread?

[TriceD]

I was thinking that the following section:

While ThreadX.ThreadState <> System.Threading.ThreadState.Aborted AndAlso ThreadX.ThreadState <> System.Threading.ThreadState.Stopped
                    System.Threading.Thread.Sleep(1)
          End While

would ensure that the function doSomething() doesn't return until ThreadX finishes running, and that line 4 therefore would not be executed before. That's obviously not the case, but what am I doing wrong? And more importantly, how do I do it right?

[Ramy Mahrous]

My opinion is to remove the initiation of the new thread in the class

Dim ThreadX As New System.Threading.Thread(AddressOf doSomethingElse)
          
          ThreadX.IsBackground = True
          ThreadX.Start()

          While ThreadX.ThreadState <> System.Threading.ThreadState.Aborted AndAlso ThreadX.ThreadState <> System.Threading.ThreadState.Stopped

rather creating this new thread in the class you call DoSomething

1- Dim str As String
2- Dim x As New myClass
3- Dim thrd As new Thread(new ThreadStart(x.DoSomthing)
' Try to modify DoSomthing to be void to work in this wasy
'4- x.closeSomething()

Or you can read more about threading, talk to thread from another, etc.. it may help http://msdn.microsoft.com/en-us/library/system.threading.thread_members.aspx

[TriceD]

Thanks for your suggestion, RamyMahrous... I was able to circumvent the problem somehow by having the instantiation of myClass in its own thread. No idea why that worked.

[Ramy Mahrous]

Let me see to learn from you, and if it solved please mark it as solved to be used as reference for people facing this problem. Thanks