Develop Reference

c# Multi threading operation triggered by a form

Good day,
After being unsuccessful in my Google & Stackoverflow queries (not sure what I should search for), I'm posting here a public question.
I have a main form (frmMainMenu). Whenever this form is loaded and a button on this form is pressed, I'm trying to update a chart. However, as this could be CPU-demanding, I was considering calling the operation to retrieve the chart from another thread.
I'm constantly getting an error : Cross-thread operation not valid: Control 'labelX2' accessed from a thread other than the thread it was created on. System.Windows.Forms at System.Windows.Forms.Control.get_Handle()
The idea behind is also to display this symbol (referenced as the circularProgress1 control whenever data is being retrieved and to hide it whenever the operation is complete.
Here below is the code of my method in the userform :
[...]
private void feedDashboard()
{
Thread l_Thread;
ClsStartPgm l_Start = null;
try
{
this.Invoke(new MethodInvoker(delegate()
{
l_Thread = new Thread(() =>
{
try
{
l_Start = new ClsStartPgm();
l_Start.getDashboardInformations(
this.labelX2,
this.circularProgress1,
this.tmr_Progress,
this.chart1,
this.expandablePanel_1);
}
finally
{
// onCompleted();
}
});
l_Thread.Start();
}));
}
catch (Exception exc)
{
ClsFinappErrorManager.manageException(exc);
}
finally
{
}
}
[...]
and if it can be helpful, here is my mentioned getDashboardInformations method of my Class ClsStartPgm
public sealed class ClsStartPgm
{
[...]
// (Constructors, accessors and other methods not mentioned here
// to simplify the reading of my question)
[...]
public void getDashboardInformations(
LabelX pInformationText,
Controls.CircularProgress pCircularProgress,
System.Windows.Forms.Timer pTimer,
Chart pChart1,
ExpandablePanel pExpandablePanel1)
{
List<double> l_DoubleList = null;
List<string> l_StringList = null;
try
{
pTimer.Start();
this.m_Busy_Dashboard_Generation = true;
this.m_Busy_Dashboard_Generation = false;
double[] yValues = l_DoubleList.ToArray();
string[] xValues = l_StringList.ToArray();
pChart1.Series["MySerie"].Points.Clear();
// Populate series data
pChart1.Series["MySerie"].Points.DataBindXY(xValues, yValues);
// Set Doughnut chart type
pChart1.Series["MySerie"].ChartType = SeriesChartType.Pie;
// Set title of the expendable panel
pExpandablePanel1.TitleText = "Situation: " + DateTime.Now.ToShortDateString();
[...]
}
catch (Exception exc)
{
ClsFinappErrorManager.manageException(exc);
}
finally
{
l_Tuple = null;
l_Accounts = null;
}
}
}
Please, could anyone guide me on what's wrong in my code? I'm definitely not asking to get the code written for me. However, I would be keen on understanding what I'm doing incorrectly here in my approach.
Many thanks for your appreciated help and best wishes,

Multiple thread not working correctly in C#

I create parallel process and DataTable dtUser have two rows, it should create two browser:
Parallel.ForEach(dtUser.AsEnumerable(), items =>
OpenBrowser(items["user"].ToString(), items["pass"].ToString()));
Lapsoft_OneDriver browser;
public void OpenBrowser(string username, string password)
{
browser = new Lapsoft_OneDriver(Browsers.Chrome);
browser.GoToUrl(link);
browser.FindElementById("txtUserName").SendKeys(username);
browser.FindElementById("txtpassword").SendKeys(password);
}
It create two Chrome process but only first process running line code block:
browser.GoToUrl(link);
browser.FindElementById("txtUserName").SendKeys(username);
browser.FindElementById("txtpassword").SendKeys(password);
The second process only initializes new browser and not do anything.
If I change this line:
browser = new Lapsoft_OneDriver(Browsers.Chrome);
to
var browser = new Lapsoft_OneDriver(Browsers.Chrome);
It's working.
But another method continues to use variable browser to execute other code.
So, I must declare global variable Lapsoft_OneDriver browser out of a function to use in another method use it.
My problem is:
Why using Lapsoft_OneDriver browser; it create two Chrome process but only first process active, it will insert to browser.FindElementById("txtUserName") two values of variable username and second process not do anything?
Updated:
When to change the code, I have any problem.
I will add more code of frmMain_Load:
private void frmMain_Load(object sender, EventArgs e)
{
thread = new LThread();
thread.StartedEvent += new LThread.startDelegate(AllCaseProgram);
numLog = int.Parse(dtSetting.Rows[0]["num_Log"].ToString());
}
int numProcess;
private void AllCaseProgram(object args)
{
try
{
switch (numProcess)
{
case 0:
Parallel.ForEach(dtUser.AsEnumerable(), items => Start(items["user"].ToString(), items["pass"].ToString()));
break;
case 1:
ClickCart();
break;
case 2:
Result();
break;
}
}
catch (Exception ex)
{
if (browser != null)
browser.Cleanup();
numProcess = 0;
AllCaseProgram(null);
}
}
At event of button StartProgram()_Click. I start Thread like: thread.Start();
You said: should be add this function to my program.
public static void Start(string user, string pwd)
{
var test = new frmMain();
test.OpenBrowser(user, pwd);
test.ClickCart();
}
My update question is:
Seem function Start(string user, string pwd) should be change to function AllCaseProgram include all switch case.
And variable numLog in frmMain_Load have values = 3. In function test.ClickCart() I also use this variable but values auto change to 0.
Have any issues with code? Thanks.
And LThread class is:
public class LThread : BackgroundWorker
{
#region Members
public delegate void startDelegate(string ID);
public event startDelegate StartedEvent;
private static int RandNumber(int Low, int High)
{
Random rndNum = new Random(int.Parse(Guid.NewGuid().ToString().Substring(0, 8), System.Globalization.NumberStyles.HexNumber));
int rnd = rndNum.Next(Low, High);
return rnd;
}
protected override void OnDoWork(DoWorkEventArgs e)
{
StartedEvent(RandNumber(100,10000).ToString()); //put whatever parameter suits you or nothing
base.OnDoWork(e);
e.Result = e.Argument;
}
BackgroundWorker bwThread;
// Main thread sets this event to stop worker thread:
public Boolean bwIsRun;
int m_time_delay = 10000;
Delegate m_form_method_run;
Delegate m_form_method_stop;
Form m_type_form;
#endregion
#region Functions
public void Start()
{
try
{
bwIsRun = true;
this.RunWorkerAsync();
}
catch { }
}
public void Stop()
{
try
{
bwIsRun = false;
}
catch { }
}
private void StartToListen(object sender, DoWorkEventArgs e)
{
while (true)
{
Thread.Sleep(m_time_delay);
if (bwIsRun == true)
{
m_type_form.Invoke(m_form_method_run);
}
else
{
BackgroundWorker bwAsync = sender as BackgroundWorker;
if (bwAsync.CancellationPending)
{
e.Cancel = true;
return;
}
break;
}
}
}
#endregion
}

You should encapsulate your state for each test run. That way you'll have a class that has the responsibility the start a browser, execute one or more actions, while keeping all the required state belonging to a single run private for just one instance, while you can have a many instances as you like (if resources permit).
// this is NOT a winform, this is a new and seperate class ...
// don't try to mix this with an WinForm, that will fail
public class BrowserTestRunner
{
// only this Test instances uses this browser
Lapsoft_OneDriver browser;
private void OpenBrowser(string username, string password)
{
browser = new Lapsoft_OneDriver(Browsers.Chrome);
browser.GoToUrl(link);
browser.FindElementById("txtUserName").SendKeys(username);
browser.FindElementById("txtpassword").SendKeys(password);
// you probably want to click on something here
}
// some other test
private void ClickCart()
{
browser.FindElementById("btnCart").Click();
}
// add other actions here
// this starts the test for ONE browser
public static void Start(string user, string pwd)
{
var runner = new BrowserTestRunner();
runner.OpenBrowser(user, pwd);
// wait for stuff, check data, prepare the next steps
// for example
// runner.ClickCart();
// other actons here
}
}
Now you can create as many Test class instances as you like, while each instance of the class manages its own internal state, without interfering with other instances:
Parallel.ForEach(dtUser.AsEnumerable(), items =>
BrowserTestRunner.Start(items["user"].ToString(), items["pass"].ToString()));
If you want to start that from your backgroundworker do:
private void AllCaseProgram(object args)
{
try
{
switch (numProcess)
{
case 0:
Parallel.ForEach(
dtUser.AsEnumerable(),
items => BrowserTestRunner.Start(items["user"].ToString(), items["pass"].ToString()));
break;
case 1:
ClickCart();
break;
case 2:
Result();
break;
}
}
catch (Exception ex)
{
if (browser != null)
browser.Cleanup();
numProcess = 0;
AllCaseProgram(null);
}
}
By all means: don't start the main form again. Just separate your WinForm from the code you use to operate the browser. That does mean that you have to move the code that interacts with the browser to the BrowserTestRunner. Don't try in keeping the logic for your selenium stuff in the WinForm class because that is doomed to fail. As you are already experiencing.

What you got here is sort of a race condition. You got two threads not getting along when handling a single field in the class. Your problem is only that you don't have sufficient space to store all the browser instances you require.
What happens is basically that the first thread enters the method, creates a instance of the chrome browser and stores it in the variable. Then the second thread enters the function and does the same thing. But it also stores the instance in the same variable. Now the first thread continues and goes to a link. But the instance it is working with is already replaced by the second thread. And so on. This may happen with the threads the other way around or the overlapping may happen after more lines where handled. But it is bound to go wrong.
The way to resolve it, is as you noticed to make the variable local by adding a var. This way both threads are working with distinct variables.
Now you said you need the variable in another function. The question is: Do you need both? Do you need only one? Do you need a specific one?
In case you need only one, you just store the variable in the global variable by adding a line like this in your function:
this.browser = browser;
So it would look like this in total:
Lapsoft_OneDriver browser;
public void OpenBrowser(string username, string password)
{
var localBrowser = new Lapsoft_OneDriver(Browsers.Chrome);
localBrowser.GoToUrl(link);
localBrowser.FindElementById("txtUserName").SendKeys(username);
localBrowser.FindElementById("txtpassword").SendKeys(password);
this.browser = localBrowser;
}
I changed the name of the local browser variable, so it gets clearer what variable is used. Do note that either one of the created browsers could end up in the variable.
In case you need a specific one you have to determine if you have the correct one and store the result after this.
If you need both you have to store them in a list. The namespace System.Collections.Concurrent offers lists that can be handled by multiple threads at once.

Form not loading correctly

I'm trying to build a TAPI based phone call system using JulMar's Atapi x86. One of the functions is to pop a specific form on an inbound call. However, whenever the form pops, it comes up incorrect, as shown below (I have tried several forms as a test and they all do the same thing). There is no error, nothing in the output window to suggest what the issue is.
Code:
private void incomingcall(object sender, NewCallEventArgs e)
{
string phonenumber = e.Call.CallerId; //get the phone number of the call
SqlCommand getincoming = new SqlCommand(Querystrings.getincomingquery(), DB);
getincoming.Parameters.AddWithValue("##TELEPHONE", phonenumber);
DataTable results = new DataTable();
try
{
DB.Open();
using (var results = getincoming.ExecuteReader())
{
results.Load(results);
}
}
catch (Exception ex)
{
Inbound ib = new Inbound(phonenumber, null);
ib.Show();
}
finally
{
DB.Close();
}
if (results.Rows.Count == 1)
{
loadcontactrequest(Convert.ToInt32(results.Rows[0].ItemArray[0]), phonenumber);
}
else
{
loadinbound(phonenumber, results);
}
}
I have loaded these forms outside of this function at other points, meaning it is something to do with this function. Does anybody know where I'm going wrong?
EDIT:
private void loadcontactrequest(int ContactID, string phonenumber)
{
ContactRequest cr = new ContactRequest(ContactID, Global.loginbound("Single customer found", phonenumber));
cr.Show();
}
These functions have been tested elsewhere and work correctly individually, I believe it might be TAPI related.
EDIT 2 - Delegate:
public static void inittapi()
{
if (TestOptions.notapi)
return;
tapi = new TapiManager("Omitted");
tapi.Initialize();
foreach (TapiLine ad in tapi.Lines) //Get all lines available to this PC
{
if (ad.Name.ToUpper().Contains("Omitted"))
{
phoneline = ad;
phoneline.Open(MediaModes.All); //Open the phone line for making and receiving calls
phoneline.NewCall += new EventHandler<NewCallEventArgs>(new TAPI().incomingcall); //Add the incoming call event handler
}
}
}

It's possible that this event is triggered on a different thread than the UI thread of your application.
Modify the method like this to test whether this is the problem:
private void incomingcall(object sender, NewCallEventArgs e)
{
Form form;
if(Application.OpenForms.Count > 0)
{
form = Application.OpenForms[0];
}
if (form != null && form.InvokeRequired)
{
form.BeginInvoke(new Action(() => { incomingcall(sender, e); }));
return;
}
// Your current code goes here
}
This will identify that we are in a different thread than your main form (form) was created on and then execute the function again on the main form's thread.

How can I bind my List<string> to a datagridView?

i am trying to display the contents of a List in a datagridview using the following code.
List<string> data = new List<string>();
dataGridView1.DataSource = data;
I am adding my data into the List in a backgroundWorker. If I change List to BindingList, I get an error saying
Cross-thread operation not valid: Control 'dataGridView1' accessed from a thread other than the thread it was created on.
however if I use List, I get a 3rd column when the datagrid is shown it which only contains the legth of the string for each entry in Categories.
Does anyone know how to get the datagrid to show the string contents instead of the string length while using a BackgroundWorker?
private void OnBackgroundWorkerDoWork(object sender, DoWorkEventArgs e)
{
importExcelFile();
}
private void importExcelFile()
{
// hard coded file name for testing.
TextFieldParser parser = new TextFieldParser(#"E:\\test.csv");
parser.TextFieldType = FieldType.Delimited;
parser.SetDelimiters(",");
while (!parser.EndOfData)
{
//Processing row
string[] fields = parser.ReadFields();
foreach (string field in fields)
{
//TODO: Process field
data.Add(field);
}
}
parser.Close();
}
private void loadFileToolStripMenuItem_Click(object sender, EventArgs e)
{
backgroundWorker1.DoWork += OnBackgroundWorkerDoWork;
backgroundWorker1.RunWorkerAsync();
}
private void OnBackgroundWorkerRunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
dataGridView1.DataSource = data;
}

You can pass list with BackgroundWorker.ReportProgress. I allows to pass progress and custom object (full dentition on MSDN). Handling this event is UI thread so it will be correct.
If you need this on the end, just use RunWorkerCompletedEventArgs.Result (again definition on MSDN)

Based on How to bind a List<string> to a DataGridView control?
I created a class
public class StringValue
{
public StringValue(string s)
{
_value = s;
}
public string Value { get { return _value; } set { _value = value; } }
string _value;
}
then changed List to List
I am getting data but it's appearing in Column 3. I am only suppose to have 2 columns.

Please create a delegate and invoke the delegate using control.Invoke
You can use Invoke like this:
private void AddToListBox(object oo)
{
Invoke(new MethodInvoker(delegate { listBox.Items.Add(oo); }));
}
More about Background Worker
Good luck!

Use this code .I also faced the similar kind of problem but sorted it out using LinQ..
IList<String> listObj = new List<String>();
dataGridView1.DataSource = listObj.Select(x => new { Value = x }).ToList();
here,
dataGridView1 :- ID of datagridview

update variable based upon results from .NET backgroundworker

I've got a C# program that talks to an instrument (spectrum analyzer) over a network. I need to be able to change a large number of parameters in the instrument and read them back into my program. I want to use backgroundworker to do the actual talking to the instrument so that UI performance doesn't suffer.
The way this works is - 1) send command to the instrument with new parameter value, 2) read parameter back from the instrument so I can see what actually happened (for example, I try to set the center frequency above the max that the instrument will handle and it tells me what it will actually handle), and 3) update a program variable with the actual value received from the instrument.
Because there are quite a few parameters to be updated I'd like to use a generic routine. The part I can't seem to get my brain around is updating the variable in my code with what comes back from the instrument via backgroundworker. If I used a separate RunWorkerCompleted event for each parameter I could hardwire the update directly to the variable. I'd like to come up with a way of using a single routine that's capable of updating any of the variables. All I can come up with is passing a reference number (different for each parameter) and using a switch statement in the RunWorkerCompleted handler to direct the result. There has to be a better way.

I think what I would do is pass a list of parameters, values, and delegates to the BackgroundWorker. That way you can write the assign-back code "synchronously" but have execution deferred until the values are actually retrieved.
Start with a "request" class that looks something like this:
class ParameterUpdate
{
public ParameterUpdate(string name, string value, Action<string> callback)
{
this.Name = name;
this.Value = value;
this.Callback = callback;
}
public string Name { get; private set; }
public string Value { get; set; }
public Action<string> Callback { get; private set; }
}
Then write your async code to use this:
private void bwUpdateParameters_DoWork(object sender, DoWorkEventArgs e)
{
var updates = (IEnumerable<ParameterUpdate>)e.Argument;
foreach (var update in updates)
{
WriteDeviceParameter(update.Name, update.Value);
update.Value = ReadDeviceParameter(update.Name);
}
e.Result = updates;
}
private void bwUpdateParameters_RunWorkerCompleted(object sender,
RunWorkerCompletedEventArgs e)
{
var updates = (IEnumerable<ParameterUpdate>)e.Argument;
foreach (var update in updates)
{
if (update.Callback != null)
{
update.Callback(update.Value);
}
}
}
Here's how you would kick off the update. Let's say you've got a bunch of member fields that you want to update with the actual values of the parameters that were used:
// Members of the Form/Control class
private string bandwidth;
private string inputAttenuation;
private string averaging;
// Later on, in your "update" method
var updates = new List<ParameterUpdate>
{
new ParameterUpdate("Bandwidth", "3000", v => bandwidth = v),
new ParameterUpdate("InputAttenuation", "10", v => inputAttenuation = v),
new ParameterUpdate("Averaging", "Logarithmic", v => averaging = v)
};
bwUpdateParameters.RunWorkerAsync(updates);
That's all you have to do. All of the actual work is done in the background, but you're writing simple variable-assignment statements as if they were in the foreground. The code is short, simple, and completely thread-safe because the actual assignments are executed in the RunWorkerCompleted event.
If you need to do more than this, such as update controls in addition to variables, it's very simple, you can put anything you want for the callback, i.e.:
new ParameterUpdate("Bandwidth", "3000", v =>
{
bandwidth = v;
txtBandwidth.Text = v;
})
Again, this will work because it's not actually getting executed until the work is completed.

[Edit - look back at update history to see previous answer. Talk about not being able to see the wood for the trees]
Is there any reason that, rather than passing a reference number to the Background Worker, you can't pass the ID of the label that should be updated with any value passed back?
So the UI adds an item in the work queue containing:
Variable to change
Attempted change
UI ID
and the BackgroundWorker triggers an event with EventArgs containing
Attempted change
Actual value after attempt
UI ID
Error Message (null if successful)
which is all the information you need to update your UI without a switch or multiple event args and without your Background Worker ever being aware of UI detail.

How about something like this?
[TestFixture]
public class BGWorkerTest
{
string output1;
string output2;
[Test]
public void DoTest()
{
var backgroundWorker = new BackgroundWorker();
backgroundWorker.DoWork += (sender, args) =>
{
output1 = DoThing1();
output2 = DoThing2();
};
backgroundWorker.RunWorkerAsync();
//Wait for BG to finish
Thread.Sleep(3000);
Assert.AreEqual("Thing1",output1);
Assert.AreEqual("Thing2",output2);
}
public string DoThing1()
{
Thread.Sleep(1000);
return "Thing1";
}
public string DoThing2()
{
Thread.Sleep(1000);
return "Thing2";
}
}