I have a word add-in, written in C#. When the user picks an option from the ribbon a custom task pane (user control) opens within the application (Word).
From this task pane, they press run, and the active document gets analyzed in a series of fairly complex ways. Checks such as interrogating any bold text in the document and many more. When running the whole process can take anything from 5 seconds to 1 minute, depending on the document. This is fine, no-one has an issue with this.
The problem comes when we try and implement a cancel button. To do this I have tried using a background worker. Everything works.... except that when communicating with the document from the thread (background worker) it is around 7-8 times slower than it was when running from the main thread. I have not been able to find much info on this, any advice or help would be greatly appreciated.
I have tried other avenues (open xml) but these are not viable options (we have to deal with .doc as well as .docx)
Thanks
To give an example:
I have a button on the taskpane (Run).
That calls private void btnRun_Click
That in turn, sets off the background worker backgroundWorker1.RunWorkerAsync();
In the do work method of the background worker, I have code such as:
myClass.Method()
In myClass would be a line of code such as:
For each Word.Field in ActiveDocument.Fields
That might take, say, 1 second to run from the main button click thread, and up to 30 seconds to run from the background worker. All other code works in good time, it is only code that accesses the Word document that seems to have problems
That's because the background thread is running is a different COM apartment than Word's STA.
Another approach you might want to consider is to show the dialog, then proceed with the processing in the same thread, having Windows messages pumped from time to time (e.g. at the beginning of long, possibly nested loops).
When the user presses the button, you set a flag, that you should check regularly throughout the code (possibly right after where you process messages).
You may need to implement UI modality yourself:
Display your window with e.g. Word as the owning window, and make sure it's focused
Disable the owning window
When you're done processing:
Enable the owning window
Close your window
Don't pump messages between steps 1 and 2 of either stage.
Related
I’ve got a process which will take a little under 5 seconds to complete. The user will most likely notice the program flicker for a few seconds after pushing the “go” button.
My question is:
Is this something that would normally be dumped onto a background worker, or is there another .NET method for handling small tasks, or is this something that shouldn’t be a concern?
FYI:
The process opens a user specified excel file, processes an unknown number of lines (max 1.5 million due to excel I believe), and queries a database (very quick query). So at the worst case scenario the user uploads a 1.5 million row excel file and is running on a very slow internet connection.
If you don't want the user to be able to do anything while the file is being uploaded, then you don't need to put it on a different thread.
If you want the user to be able to go on to other tasks while the file is uploading, put it on a different thread.
As a general rule of thumb, if I have a situation where I absolutely don't want the user to do anything while a long-running process is going, I disable the controls on the form until the task is complete, and usually use a status indicator to show that progress is happening.
My personal guideline for whether or not to allow user interaction is if the results of a process could be altered by a user action in mid-stream.
For example, one program that we have parses a bunch of queries on a highly normalized database (normalized to the point where reporting is sloooow) into "reportable" tables, and I don't want the user altering data in one of the source tables while the query is running, because it will give goofy results.
If there is no harm in allowing user interaction while the process is occuring, then put it in another thread.
Edit
Actually, on reading #UrbanEsc and #archer's comments, I agree with them. Still put it on a different thread and freeze the controls (and include a progress indicator where possible).
I would push this to a background worker. Doing so will keep the UI responsive. If the process ever does lag for more than a few seconds, users start getting nervous ...especially when the lagging process causes the UI to be 'frozen'.
From a user experience point of view it might be best to hand the job over to a different thread or an asynchronous worker and tell the user that his request is being processed in the background. Once the worker finishes, a success/failure message can be handled and shown to the user as required.
The cheapest way to handle the problem is to turn the cursor into an hourglass during the processing. That tells user please wait, I'm busy.
According to the budget (time and/or effort) you're willing to throw in it, using a backgroundworker and some reporting GUI is certainly a plus. But it's up to you according to your app.
For example, I'm currently modifying an in-house app that has 3 users. In that case, the hourglass is OK: All 3 of them will quickly learn they just have to wait. Don't get me wrong: this app is damn important. Without it, the small company that uses it would just die. But if I ask them for 2 hours of extra budget for a nice and tested little GUI, background thread, blah vs an hourglass, what do you think they'll say?
On the other hand, if it's an important operation in your flagship product, of course be nice to your users! Don't hesitate: background thread. Especially if the operation may actually take much longer than those 5 seconds.
Conclusion: Be pragmatic!
I would put it into a background worker or fire of a task if you are in .NET 4.0, for example:
void OnButtonClick(...)
{
new TaskFactory().StartNew(() => { /* your excel and query code */ });
}
I'll vote for the background worker process, since a frozen UI is like a frozen application, and most of users will think your application isn't doing anything at all.
UI thread for a progress bar or some animation, info text noticing what's going on + background worker thread = win
I think every process not related with the UI itself should be started as a separate thred or, in this case, as a bg worker. This will help to maintain the app healthy and easy to improve/fix in the future.
Also, as a user or tester, I really hate flicking and freezing windows...
Regards.
A general rule of thumb is any operation that takes a second or longer to complete requires some form of feedback to the user. This can be a progress bar, message, etc. Anything longer then that then the user becomes frustrated (not sure if they did something wrong, hate waiting, etc).
For operations like this that can take longer based on the environment (number of apps, available memory, data size, hard drive speed, etc) they should ALWAYS be put on a background thread and pipe messages back to the UI. I love the BackGroundWorker for this.
I'm writing a c# application that requires user authentication.
When the user hits the log in button, quite a bit of stuff is done in the background, but I'm having trouble informing the user that something is happening, and that the program isn't just frozen.
I have some hidden text fields that I would like to have show up after they log in, while this stuff is running, but I can't seem to get it to show up.
Basically, when the user hits the log in button, it checks to see if their credentials are correct, then the messages should show up, and then either some other functions might run, followed by a different form being shown.
After the credentials are checked, and I know that the user is valid, I tried running this:
please_wait.Visible = true;
But it doesn't change when it gets to that point in the code.
I've tried threading it, to see if that would help. Instead of calling the above line, I just start a thread that does it.
That doesn't work either. The field still doesn't show up.
If I return out of the function right after I either start the thread or change the Visible property, it works just fine.
How do I get it to work fine and have more code run after the change?
The problem isn't that you need to update the UI from a background thread. Rather, it's that you should be performing your long-running task in a background thread and marshalling updates to the foreground. This is frequently done via a BackgroundWorker with progress notification (on a progressbar, for example).
Basically, your UI foreground thread is either loaded or blocked doing work, so it isn't handling messages in its message queue to update your user interface.
Along with what Greg recommends (which is certainly the first step if you're not already doing it) you may also need to give up some quantum.
If you are taxing the scheduler, it's possible that the UI updates (which are pretty low priority) may be getting preempted until your worker is complete. Adding an Application.DoEvents (or maybe Thread.Sleep(1) in the background thread) could give the UI a little scheduler time to paint.
Have you tried adding a call to Application.DoEvents()? It's a hack, but it's all you sometimes need.
K I am looking at a primarily single thread windows forms application in 3.0. Recently my boss had a progress dialogue added on a separate thread so the user would see some activity when the main thread went away and did some heavy duty work and locked out the GUI.
The above works fine unless the user switches applications or minimizes as the progress form sits top most and will not disappear with the main application. This is not so bad if there are lots of little operations as the event structure of the main form catches up with its events when it gets time so minimized and active flags can be checked and thus the dialog thread can hide or show itself accordingly.
But if a long running sql operation kicks off then no events fire. I have tried intercepting the WndProc command but this also appears queued when a long running sql operation is executing. I have also tried picking up the processes, finding the current app and checking various memory values isiconic and the like inside the progress thread but until the sql operation finishes none of these get updated. Removing the topmost causes the dialog to disappear when another app activates but if the main app is then brought back it does not appear again.
So I need a way to find out if the other thread is minimized or no longer active that does not involve querying the actual thread as that locks until the sql operation finishes.
Now I know that this is not the best way to write this and it would be better to have all the heavy processing on separate threads leaving the GUI free but as this is a huge ancient legacy app the time to re-write in that fashion will not be provided so I have to work with what I have got.
Any help is appreciated
It sounds as if the long running operation is bound to the progress dialog? That's usually a bad idea and I wonder whether the progress can be showed at all.
However you should consider using a BackgroundWorker for your long running operations. So your GUI (the main form as well as the progress dialog stays alive).
This way you should be able to send the minimize event of the main form to the progress dialog which can react to it instantly.
Btw. the BackgroundWorker supports progress reports on its own.
I'm assuming it's possibly to do so as programs like google chrome have gone one better and put each tab on a separate process.
So how can i put a GUI control such as a datagridview on a separate thread?
That is not the control that is in a seperate thread, but the request launched through the control.
Let's say you have two tabs opened on different addresses. You click on a link that directs you to another site on the first tab. Meanwhile, you click another link on the second tab.
First, you need to know that a thread might be launched when you click the link on the first tab, making it GUI responsive. This is the same with the second tab, when you clicked the link in it.
Second, we now have one thread (the main thread, also called the GUI-thread) which job is to handle the user interaction. Another thread processing the request from the link on the first tab, and another thread from the link on the second tab.
Third, while your link requests for both tabs are being processed, you might let's say open a new tab and doing a search on Google! Then, this requires your GUI to be responsive, even while the application, the browser, is occupied with your requests.
Fourth, on the background-threads' return, they will return to the main thread reporting the result of their work, that is, the Web response they obtained requesting to solve the DNS linked the the links clicked.
An interesting way to make it possible in C#, and keeping it as easy as possible, is through the BackgroundWorker class.
Each instance of a BackgroundWorker represents a thread. So, you need to instantiate as much of BackgroundWorker as it is required by the application when a mouse-click is captured, when a user clicks a link. The request is then sent to the DoWork() event which is raised when a call to RunWorkerAsync() method is made.
Here's an interesting tutorial on how to use the BackgroundWorker
This Microsoft article explains roughly how Windows Explorer does exactly what you ask:
http://msdn.microsoft.com/en-us/library/ms741870.aspx#multi_browser
You basically have one thread per top level window and all of the events for that window are fired on the same thread.
I don't think that you'll need a Thread for every single control else you'll have a huge number of threads and then you may start to run into all sorts of trouble.
Here's a couple of websites to get you started:
http://www.albahari.com/threading/
http://msdn.microsoft.com/en-us/library/aa645740(VS.71).aspx
I'm building a UI for a program, and I can't figure out why my progress bar won't become visible after the convert button is clicked.
private void convertButton_Click(object sender, EventArgs e)
{
toolStripProgressBar.Visible = true;
...
toolStripProgressBar.Visible = false;
}
I ran into a similar problem with tkinter in Python, and I had to call a function to update the idle tasks. Is there a way to do this with windows forms without using threads?
Edit: On a side note, this is a progress bar in a toolStrip that also contains a label that gets updated with status bar text. Is there any way to get the label on the left side and the progress bar on the other instead of right next to each other on the left?
Well, there is a way to do this without using threads (Application.DoEvents) but I strongly recommend against you using it. Re-entrancy is nasty, and you really don't want the UI thread tied up at all.
Use BackgroundWorker instead - it's easy, and it's pretty much designed for progress bars. It takes the hassle out of using a separate thread and reporting progress back to the UI thread. No need for Control.Invoke etc - it takes care of that for you.
There are lots of tutorials for BackgroundWorker - it shouldn't take you too long to get going with it.
Per the question you asked for the way to do this WITHOUT threads, that is to do it with Application.DoEvents();. (Just add that call right after setting the progress bar as visible.)
Now I do agree with Jon Skeet though that BackgroundWorker is a better way of doing this, but it does use a separate thread.
You need to execute your process in a thread separate from the UI thread, and then have it periodically report back to the UI thread with it's progress. If your convert operation is working inside the UI thread, it will simply go unresponsive until the operation is complete.
The progress bar can only become visible when it is allowed to paint which occurs during the processing of messages. Message processing cannot normally happen while you are in the middle of an event handler. If you want the progress bar to show up you will have to set the visiblitity to true, start a background thread to complete the work and return from the handler.
I'm guessing the problem is that the "..." in your code is a long-running process. UI updates are not instantaneous, but must run through the message queue in windows and then be painted to the screen. The queue is pumped and painting takes place in the same thread as your events.
As a result, any long-running tasks need to be moved to a different thread. More than that, your line line of code needs to called after that thread terminates. Otherwise you set the progress bar and then immediately turn it off again.
One way to do that is with a BackgroundWorker control.
Here go two links trying to explain you how things work:
(1) (2)
Now, I will try to explain it as shortly as I can. Most of what happens inside a windows forms application happens in a single thread, usually the same thread Main() runs in. If you open Program.cs, you will see that Main() has a line that looks like the following:
Application.Run(new Form1());
If you debug the application at any moment and examine the call stack, you will see it will trace back to that Run method. This means that a Windows Forms application is in fact a continuous run of the Run method. So, what is Run doing? Run is eating a message queue through which Windows sends messages to it. Run then dispatches those messages to the correct controls, which themselves do things like add text which corresponds to the key being pressed, redraw themselves, etc. Notice that all this happens during and endless loop running alongside a single thread, so weather you are typing or simply moving the window around, loads of those messages are being passed onto the application, which in turn is processing them and reacting accordingly, all in that single thread. Controls can also send messages to themselves through the queue and even you can place messages in the pump via Control.BeginInvoke. One of the things those controls do is to raise events according to what happens. So, if you click a button, the code you've written to handle that click will ultimately and indirectly be run by the Application.Run method.
Now, what is happening with your code is that even though you are changing the visible status of your progress bar to visible and then updating its Value, you are then changing its visibility to false, all in the same method. This means that only after you leave the method, will Application.Run() be able to continue iterating and consuming the message queue, effectively asking the progress bar to update its display. When that happens, you've already left the progress bar's visibility to false, the last thing you did before exiting the method. DoEvents() is a quick and dirty workaround to your problem as it reads the messages in the queue and processes them. I don't really feel comfortable using it as it can bring reentrancy problems.
Using threads is a good solution, but I would recommend using a ThreadPool thread instead of a custom thread in this kind of situation, as I tend to use custom threads only in cases where I have a limited number of long lived threads and I need to control their life cycles. The easiest and most practical way to use threads is to use the BackgroundWorker component, even though I would recommend going through the pains of understanding how to do Windows Forms multithreading with delegates if you want to really understand what is going on.
My solution is to call refresh on the status strip.
I believe this causes the UI thread to repaint the status strip.
toolStripStatusBar1.PerformStep();
statusStrip1.Refresh();
This is for .NET 4.0. Even though this question is old it was the first I found on googling this issue.