How to wait for thread to complete without blocking UI

Question

I want my program to wait after below line

frmProgressBarObj = PullMSI.ExtractByMSIName(\"products.txt\", false);

as above method is intern

Answer 1

If you're using .NET 4.0 (with VS2012) or above, you can do this quite easily with the Task Parallel Library and async-await:

private async void button1_Click(object sender, EventArgs e)
{
    frmProgressBar frmProgressBarObj = await Task.Run(() =>
                      PullMSI.ExtractByMSIName("products.txt", false));

    MessageBox.Show(string.Format("Returned {0}", frmProgressBarObj.ToString());
}

For .NET 4, you'll need to add Microsoft.Bcl.Async.

Answer 2

I'm very surprised you haven't worked with any of these before but I would really recommend reading about threading in C# since it's fundamentally important to understand the intricacies and learning the language.

Below are three different ways you can achieve what you want:

1. Using reset events (further reading: https://msdn.microsoft.com/en-us/library/system.threading.manualreseteventslim(v=vs.110).aspx). If your C# version doesn't have the ManualResetEventSlim, replace it with ManualResetEvent and change Wait() with WaitOne()

class LockingWithResetEvents
{
    private readonly ManualResetEvent _resetEvent = new ManualResetEvent(false);

    public void Test()
    {
        MethodUsingResetEvents();
    }

    private void MethodUsingResetEvents()
    {
        ThreadPool.QueueUserWorkItem(_ => DoSomethingLong());
        ThreadPool.QueueUserWorkItem(_ => ShowMessageBox());
    }

    private void DoSomethingLong()
    {
        Console.WriteLine("Doing somthing.");
        Thread.Sleep(1000);
        _resetEvent.Set();
    }

    private void ShowMessageBox()
    {
        _resetEvent.WaitOne();
        Console.WriteLine("Hello world.");
    }
}

2) Using Task Parallel Library (TPL). Further reading: https://msdn.microsoft.com/en-us/library/dd460717(v=vs.110).aspx

class LockingWithTPL
{
    public void Test()
    {
        Task.Factory.StartNew(DoSomethingLong).ContinueWith(result => ShowMessageBox());
    }

    private void DoSomethingLong()
    {
        Console.WriteLine("Doing somthing.");
        Thread.Sleep(1000);
    }

    private void ShowMessageBox()
    {
        Console.WriteLine("Hello world.");
    }
}

3) Using Async/Await. Further reading: https://msdn.microsoft.com/en-us/library/hh191443.aspx

class LockingWithAwait
{
    public void Test()
    {
        DoSomething();
    }

    private async void DoSomething()
    {
        await Task.Run(() => DoSomethingLong());
        ShowMessageBox();
    }

    private async void DoSomethingLong()
    {
        Console.WriteLine("Doing somthing.");
        Thread.Sleep(10000);
    }

    private void ShowMessageBox()
    {
        Console.WriteLine("Hello world.");
    }
}

Also good to know: Mutex (https://msdn.microsoft.com/en-us/library/system.threading.mutex(v=vs.110).aspx), Semaphore (https://msdn.microsoft.com/en-us/library/system.threading.semaphore(v=vs.110).aspx), Lock (https://msdn.microsoft.com/en-us/library/c5kehkcz.aspx), SemaphoreSlim (https://msdn.microsoft.com/en-us/library/system.threading.semaphoreslim(v=vs.110).aspx), Monitor (https://msdn.microsoft.com/en-us/library/system.threading.monitor(v=vs.110).aspx) and Interlocked (https://msdn.microsoft.com/en-us/library/system.threading.interlocked(v=vs.110).aspx).