I have the following code:
// 1.
public void RunSQL(QuerySetup querySetup)
{
//querySetup.Users is 10
for (int i = 1; i <= querySetup.Users; i++)
{
querySetup.CurrentUser = i;
var worker = new BackgroundWorker {WorkerReportsProgress = true};
worker.DoWork += worker_DoWork;
worker.RunWorkerCompleted += worker_RunWorkerCompleted;
worker.RunWorkerAsync(querySetup);
}
}
// 2.
void worker_DoWork(object sender, DoWorkEventArgs e)
{
var querySetup = e.Argument as QuerySetup;
// Doing stuff...
e.Result = querySetup.CurrentUser;
}
// 3.
void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
Console.WriteLine("User " + e.Result.ToString() + " is done.");
}
My goal is, that at the end I get:
User 1 is done
User 2 is done
...
User 10 is done
(not in that particular order)
But I only get 10x "User 10 is done".
But why? I need to somehow mark my worker process, so that I can identify it later.
Yes, there is only 1 querySetup object here and the main loop will continuously change currentUser.
All threads will share that single object.
for (int i = 1; i <= querySetup.Users; i++)
{
querySetup.CurrentUser = i;
...
worker.RunWorkerAsync(querySetup);
}
The basic solution (if you don't need other querySetup members)
for (int i = 1; i <= querySetup.Users; i++)
{
//querySetup.CurrentUser = i;
...
worker.RunWorkerAsync(i);
}
There is only one instance of QuerySetup.
You are storing the current user on this one instance. So the current user will always be the last one in your loop.
If all your workers finish after the loop is finished, then they will all see the same global state of querySetup.CurrentUser, which is 10 at that moment.
The best approach with multithreading is not to share the state between threads (because that forces you to synchronize access to that state), but instead providing each thread function with its own copy of data. In this case, it would mean that instead of providing querySetup as data for thread function, you provide querySetup.CurrentUser
Related
Im building a little app which has a long loading time.
I want to display this loading time in a progressbar to see how long i have to wait till the programm is loaded.
I hope you understand what i want..
I tried the backgroundworker already but dont understand how to use it, in every example they use in the DoWork Event a simple
for (int i = 0; i < 100; i++)
{
//method etc here
backgroundWorker.ReportProgress(i);
}
But in my eyes this is senseless for me because this only repeats my method...
Thank you in advance!
EDIT:
private void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
Aktie dataAktie = new Aktie(aktien_name);
for (int i = 0; i < 100; i++)
{
dataAktie.ReadFromDatabase();
dataAktie.FetchData();
backgroundWorker.ReportProgress(i);
}
}
private void backgroundWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
progressBar1.Value = e.ProgressPercentage;
}
private void backgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
//Controls that have to be filled
}
But this Controls dont get data im veryyyyy confused
The following code example demonstrates the use of the ReportProgress method to report the progress of an asynchronous operation to the user.
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
// This method will run on a thread other than the UI thread.
// Be sure not to manipulate any Windows Forms controls created
// on the UI thread from this method.
backgroundWorker.ReportProgress(0, "Working...");
Decimal lastlast = 0;
Decimal last = 1;
Decimal current;
if (requestedCount >= 1)
{ AppendNumber(0); }
if (requestedCount >= 2)
{ AppendNumber(1); }
for (int i = 2; i < requestedCount; ++i)
{
// Calculate the number.
checked { current = lastlast + last; }
// Introduce some delay to simulate a more complicated calculation.
System.Threading.Thread.Sleep(100);
AppendNumber(current);
backgroundWorker.ReportProgress((100 * i) / requestedCount, "Working...");
// Get ready for the next iteration.
lastlast = last;
last = current;
}
backgroundWorker.ReportProgress(100, "Complete!");
}
** http://msdn.microsoft.com/en-us/library/a3zbdb1t%28v=vs.110%29.aspx
A BackgroundWorker and it's ReportProgress method are no magic wanda that simply shows you any progress you want, you actually have to change your code to do so.
The DoWork event handler should contain the code you want to execute in the background. Ideally this is something for progress can be measured easily. For example if you have to process 10 items then after each item you could say I'm now 10% further done. That's why the example code contains a for loop.
Your code only contains two method calls, ReadFromDatabase and FetchData. So you could simply do
dataAktie.ReadFromDatabase();
backgroundWorker.ReportProgress(50); // 50% done
dataAktie.FetchData();
backgroundWorker.ReportProgress(100); // 100% done
Obviously that not really perfect. The only way to have more accurate progress is to change the ReadFromDatabase and FetchData methods, for example let them take the BackgroundWorker object as a parameter so that they can also report progress, or provide a callback for that.
I have a method that loops through all ListViewItems and for each one I am trying to simulate a delay with this code:
lvFiles.Items[i].SubItems.Add("In-Progress");
do
{
//loop
} while(DateTime.Now <= stopTime);
lvFiles.Items[i].SubItems[7].Text = "Complete";
The problem is that the form "freezes" for x seconds as expected but the status doesn't seem to update visually until all items get looped through... then all items get marked as "complete" all at once.
What is the problem, and how can I fix this?
Withim your loop try using:
Application.DoEvents();
Edit:
As per #sa_ddam213 correct comment, it is not good to invoke it in every iteration, so you could build a counter so that it is invoked every x iterations of the loop and not with every iteration.
If all you want to do is update the UI throughout the process then this would work:
lvFiles.BeginInvoke(() => lvFiles.Items[i].SubItems[7].Text = "Complete");
I ended up using a BackgroundWorker similar to this solution substituting with updating the listview instead of a progress bar:
private void bw_DoWork(object sender, DoWorkEventArgs e)
{
BackgroundWorker worker = sender as BackgroundWorker;
for (int i = 1; (i <= 10); i++)
{
if ((worker.CancellationPending == true))
{
e.Cancel = true;
break;
}
else
{
// Perform a time consuming operation and report progress.
System.Threading.Thread.Sleep(500);
worker.ReportProgress((i * 10), "some data to pass to other thread");
}
}
}
and
private void bw_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
//listview update code here - e.Argument cast and parsed to update listview
}
I am studying parallelism and would like to know which way do you recommend for me to access other thead elements, for example, imagima I'll fill a combobox with some names, query the database I would do in parallel but I could not do a combobox.add (result) from within the task, which way do you recommend me?
a simple example to understand my question:
private void button1_Click (object sender, EventArgs e)
{
Task task = new Task (new Action (Count));
task.Start ();
}
void Count ()
{
for (int i = 0; i <99; i + +)
{
Thread.Sleep (1);
progressBar1.Value = i;
}
}
time to pass the value for the progressbar result in error
If you want to schedule a task that access UI controls, you need to pass the current synchronization context to the scheduler. If you do that the scheduler will make sure your task is executed on the correct thread. E.g.
var uiScheduler = TaskScheduler.FromCurrentSynchronizationContext();
Task.Factory.StartNew(() => {
// code that access UI controls
}, uiScheduler);
For more info see http://msdn.microsoft.com/en-us/library/dd997402.aspx
You cannot access controls on another thread directly. You must invoke them first. Read this article: http://msdn.microsoft.com/en-us/library/ms171728.aspx
This is about what is would look like if you took the article and translated it for your own use: (NOT TESTED)
delegate void SetProgressBarCallback();
private void SetProgressBar()
{
// InvokeRequired required compares the thread ID of the
// calling thread to the thread ID of the creating thread.
// If these threads are different, it returns true.
if (this.progressBar1.InvokeRequired)
{
SetProgressBarCallback d = new SettProgressBarCallback(SetProgressBar);
this.Invoke(d);
}
else
{
for(int i=0; i<99; i++)
{
Thread.Sleep(1);
progressBar1.Value = i;
}
}
}
Just a quick note... the UI in WinForms can only be updated from the UI thread. Perhaps you should consider using Control.Invoke to update your progressBar1.
Ryan's answer was correct but he put the sleep inside the invoke, that caused the program to hang. Here is a example that uses the same thing he did but it does not put the sleep in the invoke.
private void button1_Click (object sender, EventArgs e)
{
Task task = new Task (new Action (Count));
task.Start ();
}
void Count ()
{
for (int i = 0; i <99; i + +)
{
Thread.Sleep (1);
if(progressBar1.InvokeRequired)
{
int j = i; //This is required to capture the variable, if you do not do this
// the delegate may not have the correct value when you run it;
progressBar1.Invoke(new Action(() => progressBar1.Value = j));
}
else
{
progressBar1.Value = i;
}
}
}
You must do the int j = i to do variable capture, otherwise it could bring up the wrong value for i inside the loop.
I'm running the following code to start my threads, but they don't start as intended. For some reason, some of the threads start with the same objects (and some don't even start). If I try to debug, they start just fine (extra delay added by me clicking F10 to step through the code).
These are the functions in my forms app:
private void startWorkerThreads()
{
int numThreads = config.getAllItems().Count;
int i = 0;
foreach (ConfigurationItem tmpItem in config.getAllItems())
{
i++;
var t = new Thread(() => WorkerThread(tmpItem, i));
t.Start();
//return t;
}
}
private void WorkerThread(ConfigurationItem cfgItem, int mul)
{
for (int i = 0; i < 100; i++)
{
Thread.Sleep(10*mul);
}
this.Invoke((ThreadStart)delegate()
{
this.textBox1.Text += "Thread " + cfgItem.name + " Complete!\r\n";
this.textBox1.SelectionStart = textBox1.Text.Length;
this.textBox1.ScrollToCaret();
});
}
Anyone able to help me out?
Starting a thread doesn't really start the thread. Instead it schedules it for execution. I.e. at some point it will get to run when it is scheduled. Scheduling threads is a complex topic and an implementation detail of the OS, so your code should not expect a certain scheduling.
You're also capturing variables in your lambda. Please see this post (there is a section on Captured Variables) for the problems associated with doing that.
You just run into the (be me called) lambda error.
You provide the ConfigurationItem from the foreach loop directly. This leads to the fact, that all your threads get the same item (the last one).
To get this to work you have to create a reference for each item and apply this to each thread:
foreach (ConfigurationItem tmpItem in config.getAllItems())
{
i++;
var currentI = i;
var currentItem = tmpItem;
var t = new Thread(() => WorkerThread(currentItem, currentI));
t.Start();
//return t;
}
And you should also consider using a ThreadPool.
MSDN Description about how to use the ThreadPool
Short summary of differences here on SO
The problem seems to be there : () => WorkerThread(tmpItem, i)
I'm not used to Func<> but it seems to work like anonymous delegates in .NET 2.0. Thus, you may have a reference to the arguments of the WorkerThread() method. Hence, their values are retrieved later (when the thread actually runs).
In this case, you may already be at the next iteration of your main thread...
Try this instead :
var t = new Thread(new ParametrizedThreadStart(WorkerThread));
t.Start(new { ConfigurationItem = tmpItem, Index = i } );
[EDIT] Other implementation. More flexible if you need to pass new parameters to the thread in the future.
private void startWorkerThreads()
{
int numThreads = config.getAllItems().Count;
int i = 0;
foreach (ConfigurationItem tmpItem in config.getAllItems())
{
i++;
var wt = new WorkerThread(tmpItem, i);
wt.Start();
//return t;
}
}
private class WorkerThread
{
private ConfigurationItem _cfgItem;
private int _mul;
private Thread _thread;
public WorkerThread(ConfigurationItem cfgItem, int mul) {
_cfgItem = cfgItem;
_mul = mul;
}
public void Start()
{
_thread = new Thread(Run);
_thread.Start();
}
private void Run()
{
for (int i = 0; i < 100; i++)
{
Thread.Sleep(10 * _mul);
}
this.Invoke((ThreadStart)delegate()
{
this.textBox1.Text += "Thread " + _cfgItem.name + " Complete!\r\n";
this.textBox1.SelectionStart = textBox1.Text.Length;
this.textBox1.ScrollToCaret();
});
}
}
Do you really need to spawn threads manually (which is a rather expensive task) ? You could try to switch to the ThreadPool instead.
You can't assume that the threads will run in the same order they were called, unless you force it, and cause a dependency between them.
So the real question is - what is your goal ?
I think that the error is somewhere else. Here are some hints to help you debug :
Give a name containing to each thread, and display the thread name instead of the config item name :
this.textBox1.Text += "Thread " + Thread.Current.Name + " Complete!\r\n";
Display the content of config.getAllItems(), may be that some items has the same name (duplicated)
===========
Here are some additional information about multi threading with winforms:
dont create new Thread directly, use the ThreadPool instead :
ThreadPool.QueueUserWorkItem(state => { WorkerThread(tmpItem, i); });
If you really want to creat your threads, use this.BeginInvoke instead of this.Invoke your worker thread will finish sooner => less concurrent thread => better global performance
don't call Thread.Sleep in a loop, just do a big sleep: Thread.Sleep(10*mul*100);
I hope that this will help you.
Thanks to all of you!
I just implemented the threadpool, and that worked like a charm - with the added bonus of not spawning too many threads at once.
I'll have a look at the other solutions, too, but this time around the threadpool will save me from having to manually check for bozos with too many configs ;)
How can I report a string (like "now searching file. . .", "found selection. . .") back to my windows.form from a backgroundWorker as well as a percentage. Additionally, I have a large class that contains the method I want to run in the backgroundWorker_Work. I can call it by Class_method(); but i am then unable to report my percentage done or anything from the called class, only from the backgroundWorker_Work method.
Thanks!
I'm assuming WCF also have the method
public void ReportProgress(int percentProgress, Object userState);
So just use the userState to report the string.
private void worker_DoWork(object sender, DoWorkEventArgs e)
{
//report some progress
e.ReportProgress(0,"Initiating countdown");
// initate the countdown.
}
And you'll get that "Initiating countdown" string back in ProgressChanged event
private void worker_ProgressChanged(object sender,ProgressChangedEventArgs e)
{
statusLabel.Text = e.UserState as String;
}
You can use the userState parameter of ReportProgress method to report that strings.
Here's an example from MSDN:
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
// This method will run on a thread other than the UI thread.
// Be sure not to manipulate any Windows Forms controls created
// on the UI thread from this method.
backgroundWorker.ReportProgress(0, "Working...");
Decimal lastlast = 0;
Decimal last = 1;
Decimal current;
if (requestedCount >= 1)
{ AppendNumber(0); }
if (requestedCount >= 2)
{ AppendNumber(1); }
for (int i = 2; i < requestedCount; ++i)
{
// Calculate the number.
checked { current = lastlast + last; }
// Introduce some delay to simulate a more complicated calculation.
System.Threading.Thread.Sleep(100);
AppendNumber(current);
backgroundWorker.ReportProgress((100 * i) / requestedCount, "Working...");
// Get ready for the next iteration.
lastlast = last;
last = current;
}
backgroundWorker.ReportProgress(100, "Complete!");
}
Read Simple Multi-threading in Windows Forms.
It's a 3-part series.
use a delegate.