Synchronise access to a resource from the UI thread

Question

I lock on a global object in order to synchronise communication to an external device from various threads, which is working fine.

I want to user a slider control to set values which I then send to my external device, so I'm using its Scroll event to listen for changes before sending them off to the device.

The problem is, I need to lock on the global object before communicating with the device, as follows:

private void slider_Scroll(object sender, EventArgs e)
{
    lock(lockObject)
    {
        //send slider values to external device
    }
}

The above always hangs indefinitely on attempting to gain the lock. The rest of my code has been working fine, so I don't think I have a genuine race condition - I'm assuming this is happening because it's running on the UI thread and that it's a Bad Idea to block on the UI thread? I could be wrong.

However, if this is the case, I'm guessing I need to wrap the above code in a method and somehow invoke it on the 'main' thread from the UI thread?

How can I achieve this?

Answer 1

Definitely never a good idea to use lock from the main UI thread. Add a BackgroundWorker() control to the form and pass the slider value into the RunWorkerAsync() method. You can retrieve the value in the DoWork() handler via e.Argument, and safely use lock from there.