Question

I have a thread that listens for commands to my WPF application. If the WPF Application gets a command to take a screenshot the task is handed over to a “screenshotService”. I found som code to take the screenshot somewhere on the interweb, seems to work, but i havent thought it through….i cannot take this screenshot from another thread, giving this exception:

{"This API was accessed with arguments from the wrong context."}

Left to say is that the signature of my screenshot method takes a UIElement from the UI, this grid is always the same one, and is pased to the constructor of the takeScreenshot method.

How would I go around and take this screenshot?

Answer 1

Use a Dispatcher or a BackgroundWorker to do the job:

ThreadStart start = delegate()
{
   Dispatcher.Invoke(DispatcherPriority.Normal, 
                new Action<string>(TakeScreenshot), 
                "From Other Thread");
};

new Thread(start).Start();







BackgroundWorker _backgroundWorker = new BackgroundWorker();

_backgroundWorker.DoWork += _backgroundWorker_TakeScreenshot;


_backgroundWorker.RunWorkerAsync(5000);

void _backgroundWorker_TakeScreenshot(object sender, DoWorkEventArgs e)
{
}