Multithreading: Communication from Parent thread to child thread
- by Dennis Nowland
I have a List of threads normally 3 threads each of the threads reference a webbrowser control that communicates with the parent control to populate a datagridview. What I need to do is when the user clicks the button in a datagridviewButtonCell corresponding data will be sent back to the webbrowser control within the child thread that originally communicated with the main thread. but when I try to do this I receive the following error message
'COM object that has been separated from its underlying RCW cannot be used.'
my problem is that I can not figure out how to reference the relevant webbrowser control. I would appreciate any help that anyone can give me.
The language used is c# winforms
.Net 4.0 targeted
Code sample:
The following code is executed when user click on the Start button in the main thread
private void StartSubmit(object idx)
{
/*
method used by the new thread to initialise a 'myBrowser' inherited from the webbrowser control each submitters object is an a custom Control called 'myBrowser'
which holds detail about the function of the object eg:
*/
//index: is an integer value which represents the threads id
int index = (int)idx;
//submitters[index] is an instance of the 'myBrowser' control
submitters[index] = new myBrowser();
//threads integer id
submitters[index]._ThreadNum = index;
// naming convention used 'browser' +the thread index
submitters[index].Name = "browser" + index;
//set list in 'myBrowser' class to hold a copy of the list found in the main thread
submitters[index]._dirs = dirLists[index];
// suppress and javascript errors the may occur in the 'myBrowser' control
submitters[index].ScriptErrorsSuppressed = true;
//execute eventHandler
submitters[index].DocumentCompleted += new WebBrowserDocumentCompletedEventHandler(DocumentCompleted);
//advance to the next un-opened address in datagridview the navigate the that address
//in the 'myBrowser' control.
SetNextDir(submitters[index]);
}
private void btnStart_Click(object sender, EventArgs e)
{
// used to fill list<string> for use in each thread.
fillDirs();
//connections is the list<Thread> holding the thread that have been opened
//1 to 10 maximum
for (int n = 0; n < (connections.Length); n++)
{
//initialise new thread to the StartSubmit method passing parameters
connections[n] = new Thread(new ParameterizedThreadStart(StartSubmit));
// naming convention used conn + the threadIndex ie: 'conn1' to 'conn10'
connections[n].Name = "conn" + n.ToString();
// due to the webbrowser control needing to be ran in the single
//apartment state
connections[n].SetApartmentState(ApartmentState.STA);
//start thread passing the threadIndex
connections[n].Start(n);
}
}
Once the 'myBrowser' control is fully loaded I am inserting form data into webforms found in webpages loaded via data enter into rows found in the datagridview. Once a user has entered the relevant details into the different areas in the row the can then
clicking a DataGridViewButtonCell that has tha collects the data entered and then has to be send back to the corresponding 'myBrowser' object that is found on a child thread.
Thank you
