I have a task running in backgroundworker. on clicking the start button user starts the process and have got one cancel button to cancel the processing.
When user clicks on cancel, I would like to show a message box that "Process has not been completed , do you want to continue".
Here I want the processing which is left to be done only after user input. Till then want to halt the back ground thread. Can anyone help me on this. Is there anyway to halt the background worker for some time .Any kind of help will be appreciated.
Not built in. You could tell your code to (on every [n] loop iterations, etc) check something like a ManualResetEvent to see if it should keep running (at the same time it checks for cancellation). I don't recommend suspending the thread (Thread.Suspend), since you don't know what locks etc it may hold at the time.
On the other hand... why not let it run until you know it should be cancelled? Then you just need to check for cancellation (there is a flag for this) every [n] iterations...
If the BackgroundWorker is working on an object that is visible to both threads, you could 'lock' that object while waiting for the user to answer the question in a dialog box. This will cause the worker's thread to halt until the dialog-generating thread ends the lock.
Related
Using System.Threading.Thread.Sleep( ) makes the entire application stop for the time taken in the arguments. I want other processes running while one process is waiting for a particular amount of time. To put it in short, I want another way other than System.Threading.Thread.Sleep( ) in my application that does not stop the entire thing.
Example: If I have a label that changes text every 5 seconds, I should be able to press a button which can do some other process, like changing an image.
Thread.Sleep() only puts the current thread to sleep. If it is the UI thread, this might block your application and it looks like it is completely blocked. Background threads are still running.
If you want to sleep without blocking, you could use the following code:
await Task.Delay(5000);
// continue here with your code, such as updating your label
This doesn't block the UI thread, just delays the proceeding of your function. You have to declare your method as async
I am not too informed about this so I am not sure this is the best way to do it
The Task.Wait Method
like that your main thread waits for the child thread to complete before continuing. From here on to your problem I guess just brains will help
an other helpful link:
Thread Synchronization
I have read a lot on threading but can't figure out a way to make this one work right. So it should really be obvious how to do this as it usually is with me (always missing the obvious) :p
Here's my problem (BTW, am working with WPF in C#):
I have a long running process i'm running on a separate thread while the UI stays responsinve and showing evolution. However, mid-process, i need to ask the user to confirm a value before proceeding. That's what i can't figure out, cause the window to confirm the value must be run in the UI thread and still return the value to the work thread so it can continue it's work.
So...
Long running process beeing run in work thread
Work thread waits for UI Thread
UI thread shows the confirmation window
User confirms/fixes value and closes the confirmation window
UI thread sends result from confirmation window to work thread
work thread gets values from UI Thread (value was changed by user? to what?)
work thread continues long running process
Work thread gets values from confirmation window
I've already the work thread working well using ThreadPool - although am open to using threading in different ways (NET 4.5). Problem i am having is that if i send the confirmation window part to dispatcher my work thread won't wait for the results from the confirmation window. If i don't put in the dispatcher i get an exception about not beeing in an STA thread when the window constructor is called.
Any ideas welcome
You probably don't want to block the worker thread waiting on UI (not saying you couldn't do it, but it would be messy).
A much simpler solution would be to split up your process into two threads; one that runs pre-user input, and one that runs after. You would prompt the user upon the first thread's completion (via a callback or event).
Something like (pseudo-code)
InitialThreadObject.Completed += () =>
{
PromptForUI();
SecondThreadObject.Start();
}
InitialThreadObject.Start();
Obviously you would choose the completion notification mechanism based on your current code.
I have a program which does some copy jobs (via File.Copy) that could last a few minutes. When the user brings another window to foreground in this time the program window gets blank since it doesn't redraw itself.
Now I want to show a ProgressBar in an extra window in the center of the screen, but that window get's blank too.
So I startet it in another thread which didn't help.
I'm quite sure someone did this before but I cannot find a working example. Any Ideas?
There is nice example in the documentation on BackgroundWorker class.
ChrisF is correct. Your long operation should be done in a BackgroundWorker thread. You can use BackgroundWorker to report progress, and hook that up to a progress bar on your form.
You need to thread your operation using a BackgroundWorker. There are other ways to thread the operation, but this one is probably the simplest, and will continue to perform message pumping in the foreground so Windows doesn't think your application has stopped responding.
Another option would be to use a Thread, and use Thread.Join to wait for the background task to complete, since Thread.Join also sends standard message pump information to Windows while it waits.
You can use BackgroundWorker class.
See this answer.
I have a code that executes for some time on GUI thread (to simplify things, let's assume in Button_Click event).
When the method starts I'd like to show a message "Please wait", and continue working. When the work is done I'll hide the message and continue.
I know I can do this with BackgroundWorker (or any other Thread related), but I was hoping there's something already finished like:
MBox.Show("Please wait...");
//do my work...
MBox.Hide();
If you have some long running process, you should not be doing this in the UI thread. What is wrong with BackgoundWorker? That class is great! I would recommend that you use that if this is a WinForms app.
If you using .Net 4 you can run a Task to work with your background worker, else you can do threading, but they shouldn't be in same thread.
You could create your own form to do this. There is nothing inherently evil about making the user wait if they would expect to wait or are required to wait. We have applications where the normal work flow requires a short wait. Placing it in a background thread doesn't help the user since they still need to wait for the operation to finish before they can do anything else.
How do I keep my C# form that, lets say is in a for-loop, from locking up? Do I call Application.DoEvents(); before the loop or after? From what I've heard using the DoEvents method will keep my app from locking.
You should not use Application.DoEvents() in order to keep your application responsive.
Calling this method will allow any waiting windows messages to be dispatched. This means if a user clicks on a button (or performs any other user interaction) that action will be processed. This can therefore cause reentrancy. If they press the same button as the one that caused the loop you are processing you will end up having the routine called again before you have finished!
Instead you should use a BackgroundWorker thread to perform the long process and then once the action is completed perform whatever additional actions are required. For example, once a button is pressed you would start the worker thread and then disable you button so it cannot be pressed again. Once the worker thread completes you would enable the button again.
There are a few ways, this (DoEvents) just forces the message pump to process messages. Some people put a Thread.Sleep at the end of a loop (always inside the loop though) in a thread. What exactly are you doing in your thread, because there might be a better way to accomplish your goal overall?
If the process is causing the UI to lock up for an unacceptable amount of time, try using a seperate thread (either create it, use the thread pool, or use the BackgroundWorker class.