Question

I can see from my debug messages that e.Result equals to “Success” all the way through the DoWorker method, but at the beginning of the RunWorkerCompleted method e.Result returns nothing at all.

This is the __construct for the WinForm

public LicenseValidator()
{
    // Initialize the UI
    InitializeComponent();

    // Start the background worker
    BackgroundWorker worker = new BackgroundWorker();
    worker.DoWork += new DoWorkEventHandler(worker_DoWork);
    worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);
    worker.RunWorkerAsync();

    // Tell debug log that the UI thread is still processing
    Debug.WriteLine("UI thread running");  
}

And here is my worker_DoWork method

public async void worker_DoWork(object sender, DoWorkEventArgs e)
{
    // Tell debug log that the worker thread is now running
    Debug.WriteLine("Worker thread running");

    // Define variables
    String HWID = Security.FingerPrint.Value();
    String APIPath = "http://xxxxxxxxx.net/api.php";
    String Serial;
    HttpClient client = new HttpClient();
    HttpResponseMessage response;
    String responseString;

    // Check for license in AppData
    try{
        // Get license path
        String licensePath = Environment.GetEnvironmentVariable("APPDATA") + @"\UniLeech\License.txt";
        // License exists, validate it
        if (File.Exists(licensePath))
        {
            Serial = File.ReadAllText(licensePath);
            Debug.WriteLine(Serial);
            response = await client.GetAsync(APIPath + "?hwid=" + HWID + "&serial=" + Serial);
            responseString = await response.Content.ReadAsStringAsync();
            Debug.WriteLine(responseString);
            dynamic jObj = JsonConvert.DeserializeObject(responseString);
            if (jObj.success == "true")
            {
                Debug.WriteLine("License validation was successful");
                e.Result = "Success";
            }
            else
            {
                e.Result = jObj.error;
            }
            Debug.WriteLine(e.Result);
        }
        // License does not exist, prompt for one
        else
        {
            Debug.WriteLine("License file not found");
            e.Result = "Unregistered";
        }
    }

Finally my worker_RunWorkerCompleted method

public void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    Debug.WriteLine("Worker completed");
    String result = e.Result as String;
    if ((e.Error == null))
    {
        Debug.WriteLine("No errors");
        Debug.WriteLine("Result = " + result);
        if (e.Cancelled)
        {
            Debug.WriteLine("Worker cancelled");
        }
        switch ((String)e.Result.ToString())
        {
            case "Success":
                this.Hide();
                this.ShowInTaskbar = false;
                Main mainForm = new Main();
                mainForm.Show();
                break;

            case "Banned":
                popupError("ERROR: License revoked!",
                           "Your license has been revoked, contact Time Sheep for more information. You can purchase a new one by visiting the ordinary order link."
                          );
                break;

            case "Invalid":
                popupError("ERROR: Invalid serial/HWID",
                           "Either your serial number or hardware identifier was invalid. If you purchased UniLeech, please contact Time Sheep with proof of purchase."
                          );
                break;

            case "Unregistered":
                this.Hide();
                this.ShowInTaskbar = false;
                Register registerForm = new Register();
                registerForm.Show();
                break;

            default:
                MessageBox.Show((string)e.Result, "ERROR");
                break;
        }
    }
}

On execution the following debug messages appear (Case: I have the file and e.Result should be “Success”):

UI thread running
Worker thread running
0123-1234-1234 (The value of Serial)
Worker completed
No errors
{"success": "true","action": "validate","error": "None"} (Returned from web API)
License validation was successful
Success
RunWorkerCompleted finished

I suspect the issue is caused by the DoWork method being asynchronous, but I don’t know how to use HttpClient synchronously.

Answer 1

You can’t have an async DoWork. BackgroundWorker assumes that when DoWork returns, it is completed.

You don’t need BackgroundWorker at all. Just use Task.Run instead.