Question

I have the following code, in which I’m trying to process a large amount of data, and update the UI. I’ve tried the same thing using a background worker, but I get a similar issue. The problem seems to be that I’m trying to use a class that was not instantiated on the new thread (the actual error is that the current thread doesn’t “own” the instance). My question is, is there a way that I can pass this instance between threads to avoid this error?

DataInterfaceClass dataInterfaceClass = new DataInterfaceClass();

private void OutputData(List<MyResult> Data)
{            
    progressBar1.Maximum = Data.Count;
    progressBar1.Minimum = 1;
    progressBar1.Value = 1;

    foreach (MyResult res in Data)
    {                       
        // Add data to listview
        UpdateStatus("Processing", res.Name);

        foreach (KeyValuePair<int, string> dets in res.Details)
        {
            ThreadPool.QueueUserWorkItem((o) =>
            {
                // Get large amount of data from DB based on key
                // – gives error because DataInterfaceClass was
                // created in different thread.
                MyResult tmpResult = dataInterfaceClass
                    .GetInfo(dets.DataKey);

                if (tmpResult == null)
                {
                    // Updates listview
                    UpdateStatus("Could not get details", 
                        dets.DataKey); 
                }
                else
                {
                    UpdateStatus("Got Details", dets.DataKey);
                }

                progressBar1.Dispatcher.BeginInvoke(
                    (Action)(() => progressBar1.Value++));
            });
        }
    }
}

EDIT:

DataInterfaceClass is actually definated and created outside of the function that it is used in, but it is an instance and not static.

Answer 1

UPDATE:
You seem to have modified the posted source code, so…

You should create an instance of the DataInterfaceClass exclusively for each background thread or task. Provide your task with enough input to create its own instance.

That being said, if you try to access data in a single database in a highly parallel way, this might result in database timeouts. Even if you can get your data access to work in a multithreaded way, I would recommend limiting the number of simultaneous background tasks to prevent this from occurring.

You could use a Semaphore (or similar) to ensure that no more than a certain amount of tasks are running at the same time.