.Net Thread Execution

Question

I have written a thread which I've started using the start method but I'm not able to know when the thread has done executing the method and destroy the thread object.

_ProgressThread = New Thread(AddressOf ExecProc)
_ProgressThread.IsBackground = False
_ProgressThread.Start()

//the flow of execution should come here only after the thread has executed the method
//but its coming and executing this line after the thread has started.
 Me.MainInit()
_ProgressThread = Nothing

What is the best method. Please help. Also I want to call a method after the thread has done executing the mehtod.

Answer 1

Firstly, setting a variable to Nothing doesn't destroy the object.

Secondly, if this is an instance variable but you don't need it after starting the thread, why keep it around at all? If it's a local variable, just let it fall out of scope.

Basically, it's not up to you to "destroy" the object - it's up to you to only keep a reference to it as long as you're interested in it.

If this doesn't help, please provide more details.

Answer 2

There are two (or more) possible ways. One is to use a ManualResetEvent as follows:

_Event = New ManualResetEvent(False); <-- Create event globally

Then, in your thread's start code:

_ProgressThread = New Thread(AddressOf ExecProc)
_ProgressThread.IsBackground = False
_ProgressThread.Start()

//the flow of execution should come here only after the thread has executed the method
//but its coming and executing this line after the thread has started.
_Event.WaitOne(); <-- This waits!
_Event.Close();   <-- This closes the event

Me.MainInit()
_ProgressThread = Nothing

In your thread method, you must call _Event.Set() before the method returns in all cases, otherwise your application will be blocked.

Another way would be to have to thread invoke a delegate when finished. The code that you want to execute after the thread is done (Me.MainInit()) would then go into the delegate method. This is actually quite elegant.

For example:

public delegate void ThreadDoneDelegate();

private void ExecProc()
{
    ThreadDoneDelegate del = new ThreadDoneDelegate(TheThreadIsDone);

    ... // Do work here

    this.Invoke(del);
}

private void TheThreadIsDone()
{
    ... // Continue with your work
}

Sorry, I do not speek VB fluently, so you'll have to convert this little C# snippet :-)

Answer 3

Hi.

If I understood it correctly, you want to wait for a thread to finish. This can be acomplished by joining the thread:

_ProgressThread = New Thread(AddressOf ExecProc)
_ProgressThread.IsBackground = False
_ProgressThread.Start()

// you can do parallel work here

// wait for the thread to finish
_ProgressThread.Join();