I have been trying to implement a BackgroundWorker into my application, and so far, it has not gone well. On a new thread, I want to open up a new Form that will have a progressbar and a label to report progress, however, this is not working well. When I call ShowDialog, the application does not respond any more. Is this because my code is running from my Form1, and I am showing WorkingForm? Also, can this be implemented cleaner?
private void button14_Click(object sender, EventArgs e)
{
List<object> param = new List<object>();
object[] objectparams = new object[1];
objectparams[0] = null;
Opera opera = new Opera();
System.Reflection.MethodInfo clearOpera = opera.GetType().GetMethod("ClearOpera");
param.Add(clearOpera);
param.Add(opera);
param.Add(objectparams);
backgroundWorker1.RunWorkerAsync(param);
}
private void button2_Click_1(object sender, EventArgs e)
{
Browser.cancelPending = true;
}
private delegate void getnewform();
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
mainForm main = new mainForm();
TestURLGUI4.Form1 form = (TestURLGUI4.Form1)Application.OpenForms[0];
var variab = (bool)form.Invoke(new getnewform(main.AskForConfirmation));
List<object> param = e.Argument as List<object>;
List<object> result = new List<object>();
var method = param[0] as MethodInfo;
object[] parameters = param[2] as object[];
if (parameters[0] == null)
{
result.Add(method.Invoke(param[1], null));
result.Add(false);
}
else
{
result.Add(method.Invoke(param[1], parameters));
if (parameters.Contains(true))
result.Add(true);
}
int progress = (100 * Browser.progressValue) / Browser.progressMax;
backgroundWorker1.ReportProgress(progress);
// If the BackgroundWorker.CancellationPending property is true, cancel
if (backgroundWorker1.CancellationPending)
{
Console.WriteLine("Cancelled");
Browser.cancelPending = true;
}
e.Result = result;
}
private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
TestURLGUI4.WorkingForm form = (TestURLGUI4.WorkingForm)Application.OpenForms[1];
form.progressBar1.Value = e.ProgressPercentage;
form.label1.Text = Browser.progressValue + "/" + Browser.progressMax;
Application.DoEvents();
}
private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
List<object> param = e.Result as List<object>;
if (e.Cancelled == false && param.Contains(true))
{
Display.DisplayURLs(param[0] as SortableBindingList<URL>);
TestURLGUI4.WorkingForm form = (TestURLGUI4.WorkingForm)Application.OpenForms[1];
MessageBox.Show("Done");
}
else if (e.Cancelled == false && param.Contains(false))
{
TestURLGUI4.WorkingForm form = (TestURLGUI4.WorkingForm)Application.OpenForms[1];
MessageBox.Show("Done");
}
}
public class mainForm
{
public void AskForConfirmation()
{
TestURLGUI4.Form1 form = (TestURLGUI4.Form1)Application.OpenForms[0];
var workingForm = new TestURLGUI4.WorkingForm();
workingForm.ShowDialog(form);
workingForm.DialogResult = DialogResult.None;
}
}
Edit: Ok, I have updated my code according to the suggestions, and now, this produces a stackoverflowexception in System.Windows.Forms.dll:
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
mainForm main = new mainForm();
TestURLGUI4.Form1 form = (TestURLGUI4.Form1)Application.OpenForms[0];
List<object> param = e.Argument as List<object>;
List<object> result = new List<object>();
var method = param[0] as MethodInfo;
object[] parameters = param[2] as object[];
if (parameters[0] == null)
{
result.Add(method.Invoke(param[1], null));
result.Add(false);
}
else
{
result.Add(method.Invoke(param[1], parameters));
if (parameters.Contains(true))
result.Add(true);
}
int progress = (100 * Browser.progressValue) / Browser.progressMax;
backgroundWorker1.ReportProgress(progress);
// If the BackgroundWorker.CancellationPending property is true, cancel
if (backgroundWorker1.CancellationPending)
{
Console.WriteLine("Cancelled");
Browser.cancelPending = true;
}
e.Result = result;
}
private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
TestURLGUI4.Form1 form1 = (TestURLGUI4.Form1)Application.OpenForms[0];
if (Application.OpenForms.Count >= 2)
{
TestURLGUI4.WorkingForm form2 = (TestURLGUI4.WorkingForm)Application.OpenForms[1];
form2.progressBar1.Value = e.ProgressPercentage;
form2.label1.Text = Browser.progressValue + "/" + Browser.progressMax;
Application.DoEvents();
}
else if(Application.OpenForms.Count == 1)
{
var workingForm = new TestURLGUI4.WorkingForm();
workingForm.ShowDialog(form1);
}
}
The purpose of a BackgroundWorker
is to invoke code on another thread (not the UI thread). By calling Invoke
in the DoWork
method, you're completely circumventing the purpose of BackgroundWorker
. Do all your UI work before you start the worker. If you need to interact with the user while the worker is working, do it in the ProgressChanged
handler--it runs on the UI thread and you don't need to use Invoke
in ProgressChanged
.
By invoking UI work in DoWork
, you run the risk of a deadlock, which will hang your program