How can I check if previously running ProgressChanged has finished in DoWork event in c#

Question

Here is a scenario, its a winforms application where I have a collection of processes which i'm running one by one inside a for-loop in the DoWork event of Backgroundworker class. And I call ReportProgress() periodically in the for-loop to update UI.

Now when I call ReportProgress() it triggers ProgressChanged event where I have the code to update the UI with all the message I have set previously in DoWork. But as this runs in a separate thread, the control goes in parallel in DoWork, but I want to hold/wait the for-loop for sometime until the previously running ProgressChanged event.

Currently, I'm calling Thread.Sleep(1000) in for-loop before executing any operation in it (like picking up the next process and running it) and this code is giving me desired output. So I just wanted to check if there is any alternative solution where (I don't use Thread.Sleep instead) I can verify/ wait the for-loop until the previously running ProgressChanged event has finished its job, and only then I proceed to run the next process from the collection in for-loop.

Answer 1

Without addressing the issues with your overall design, the way you would do this is with a semaphore. The most basic example would be:

static Semaphore _semaphore = new Semaphore(0,1);
WorkStatus _workStatus;

void DoWork()
{
    _semaphore.WaitOne();
    try
    {
        _workStatus = Foo();  //Only one thread will be able to execute this at a time
    }
    finally
    {
        _semaphore.Release();
    }
}

void HandleProgressChanged()
{
    _semaphore.WaitOne(); //Wait for any DoWork threads to finish
    try
    {
        DisplayProgress(_workStatus);
    }
    finally
    {
        _semaphore.Release();
    }
    Task.Run(DoWork);
}