I have some WinForms in my application.
On some form , I am loading other forms which have lot of data to show.
So when I click a button to load these forms they take, 9-10 seconds to load,
I wana improve this. I have heard about Background thread but don't know how to use this.
Means on the button click what should i do so that I can see my form imidiately and the processing is done by background thread ?
Please guide me so that I can improve my UI.
Getting the form to show immediately, should be fairly simple and you don't need a background thread to do it.
My guess is that you are retrieving all that data prior to loading the form or you are retrieving the data on the same thread that loads the form. You should be able to call the form with the data it needs to retrieve the rest of the data (such as ID's).
Then you just need to find a way for the data processing to happen on a thread other than the thread that creates the form.
This may not be the most elegant solution, but it gets the job done. It uses a System.Windows.Forms.Timer
private void Form1_Load(object sender, EventArgs e)
{
timer1.Start();
}
private void timer1_Tick(object sender, EventArgs e)
{
timer1.Stop();
//fill controls with data
}
If you have several sets of data that you are retrieving, you may want to consider setting up a queue of tasks to retrieve each set.
Any way that you do it. Make sure to disable any buttons(or other ui) that could cause errors if the data is not loaded.
Edit: It should be noted that winform controls don't always play nice with threads. The nice thing about the System.Windows.Forms.Timer (as opposed to System.Timers.Timer)is that it designed to play nice with controls.
BackgroundWorker are easy to use. Mainly you subscribe to DoWork event, this is where you'd put your work that will be done in a seperate thread. And you also subscribe to RunWorkerCompleted event. This will get raised when your DoWork has completed.
In this method you'd simply bind the data fetched by the DoWork method.
You can use the DoWork eventarg to pass data between DoWork and RunWorkerCompleted.
You can also cancel the work and also the you can use the RunWorkerCompleted eventArg to get the data from the DoWork and also inspect the Error property for exception handling.
IF you have lots of data, you can use a batching process, to get data per batch and display them into your UI. You can show how many total records will be fetch and the progress of it 100 out of 1000 have been loaded, 200 out of 1000 have been loaded etc, to keep the user informed. You could also provide a Cancel option so the user can stop the fetch.
In your button click you'd simply call myBackgroundWorker.RunWorkerAsync().
this will call your DoWork Handler which will be done in a seperate thread not the main UI Thread, so your UI will not FREEZE during the background worker DoWork.
The backgroundworker also support report progress.
If your problem is the main form Freezing, what you need is to collect the data on a separated Thread than the Main form is running.
To achieve that, you can do something like this:
BackgroundWorker worker;
public Form1()
{
InitializeComponent();
worker = new BackgroundWorker();
}
private void button1_Click(object sender, EventArgs e)
{
worker.DoWork += new DoWorkEventHandler(worker_DoWork);
worker.RunWorkerAsync();
}
void worker_DoWork(object sender, DoWorkEventArgs e)
{
//Collect data and open your second form here;
}
Related
I have a application that adds items queried from SQL into a list box on my main WPF form. The query takes a long time so I added it to its own thread. I have another thread that shows a new form with a please wait gif animation on it.
So in total I have 3 threads.
Main GUI thread
Thread running SQL query - thread named sql_thread
Thread opens/shows new instance of please wait form with Gif animation on it. - thread name please_wait_thread
I want the ability to cancel the thread running the SQL query from a cancel button on the please_wait_thread that shows a form with a please wait Gif animation.
I am having a real hard time understanding inheritance and how to reference objects between forms. I know how to create new instances of them but not make them communicate.
If I put the below code in the please_wait form and type sql_thread it cannot see the sql thread.
public void Cancel_btn_Click(object sender, EventArgs e)
{
sql_thread.abort();
}
How can I stop the sql_thread in it's tracks when I close the please_wait form?
The code to create the sql_thread on the main form is below.
private void btn_search_Click(object sender, EventArgs e)
{
Thread sql_thread = new Thread(sql_search_method);
}
P.S. I already tried a backgroundworker but it did not work and once it hits the long query there is no way to stop it until its done with a backgroundworker.
I have a Console app that displays a WinForms Form.
In the Form, the user clicks button 1 and it runs a long subroutine. I want to have a button 2 that can kill the subroutine at any point. However, the UI freezes when I click button 1 until the subroutine has finished. How can I get the UI to not freeze?
Your long-running code is blocking the UI thread, so you can no longer click the second button, nor interact with the UI in any way until the code is finished executing.
You'll need to move your long-running code to a separate thread. There are various (and newer) ways of doing this, but one way is the BackgroundWorker. It's pretty easy to learn, and wraps some nice functionality, like cancelling the thread.
Here's a short WinForms app to demonstrate. You have to explicitly enable the ability for the thread to be cancelled. In this example, the while loop continues indefinitely, but checks every 100ms to see if there's a request for it to be cancelled. When you click the second button, the cancellation request is sent, and the thread ends.
public partial class Form1 : Form
{
private BackgroundWorker bg;
public Form1()
{
InitializeComponent();
bg = new BackgroundWorker
{
WorkerSupportsCancellation = true
};
bg.DoWork += (sender, args) =>
{
while (true)
{
Thread.Sleep(100);
if (bg.CancellationPending)
break;
}
MessageBox.Show("Done!");
};
}
private void button1_Click(object sender, EventArgs e)
{
bg.RunWorkerAsync();
}
private void button2_Click(object sender, EventArgs e)
{
bg.CancelAsync();
}
}
Following up on chouaib's comment, another nice thing about using the BackgroundWorker in a WinForms environment is that you can drop and drop it onto your designer, similar to a Menu, Timer, etc. You can then access its members in the "properties" panel, setting "WorkerSupportsCancellation" to true, subscribing to events, etc.
From your comment:
"is there a way to run this background process and be able to update the main userform? I keep getting the "cross-thread operation not valid control accessed from a thread other than the..." I want to run the long-running background operation, and have it update the main UI with text in a label (like a percentage of its progress)"
If you want to update the UI while the thread is running, you should do that from the ProgressChanged event. First, enable that option and subscribe to the event:
bg.WorkerReportsProgress = true;
bg.ProgressChanged += bg_ProgressChanged;
Then call ReportProgress() when you want to update the UI. You could pass back a percentage complete and some text, for instance:
bg.ReportProgress(50, "Almost there...");
Finally, update the UI from inside the event:
void bg_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
var message = e.UserState.ToString();
var percent = e.ProgressPercentage;
lblStatus.Text = message + " " + percent;
}
You need to make it multithreaded as suggested in the comments. The older way of doing this was manage your own thread. Then along came the background worker (cheap and easy). Now a days you have other options such as the Task Library.
Remember - anything the runs on the UI thread prevents the UI from sending and receiving events until that operation is finished.
Look into the BackgroundWorker component
On a button press I call a background worker to change the colour of some text, and in the DoWork method it creates a new object and executes one of its methods. Here is the code:
private void StartProcessButton_Click(object sender, EventArgs e)
{
FirstTimeBackgroundWorker.RunWorkerAsync(GenKeyLabel.ForeColor = Color.DodgerBlue);
}
And the DoWork method...
private void FirstTimeBackgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
KeyFile k = new KeyFile();
k.CreateDummyFile(DLetter);
}
[The CreateDummyFile effectively does a bunch of file processing, such as copying,deleting and creating files (up to 4.0MB). Throughout I call the ReportProgress method and change some GUI elements on the form, however as it does it in one chunk I cant see the constant progress or the GUI elements change]
Now it does what its supposed to inside the CreateDummyFile method, however it executes it as if it wasn't in another thread (like when you press a button to do something and the form would freeze, and then just show the final result). Any ideas why this is? What I am doing wrong?
There is a lot of code in that class that gets executed so I can't just place it inside the DoWork method.
EDIT: Removed all of the ReportProgress's and it still only changes one of my GUI elements. (All I do is change the font.forecolour. Apart from this I am changing the text on a status strip...
You need to add the FirstTimeBackgroundWorker_DoWork as a handler of DoWork event on BackgroundWorker:
FirstTimeBackgroundWorker.DoWork += FirstTimeBackgroundWorker_DoWork;
Also make sure if you're calling back the UI to update it to do so on the UI thread, not from the background one.
I am making my first ever C# GUI. It is using a BackgroundWorker to run a computationally heavy simulation. Periodically, the simulation reports (through the ProgressChanged event) a sizable body of information that needs to be displayed in the GUI.
The GUI is divided into controls and I want each control to know how to 'update itself'.
In my research, I found lots of ways I might be able to do this.
I could think of was to have the method bougnd to ProgressChanged call an update method on each part of the GUI.
I could Invalidate the GUI and bind each controls update method to the Validating event.
I could bind each control's update method to the ProgressChanged event.
I could have each control implement the INotifyPropertyChanged interface (but I'm skeptical that this would work)
Of all of these options, which one is best practices for updating the entire GUI upon the ProgressChanged event? (or am I out in left field?)
From comment:
private void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
Simulation simulation = new Simulation();
while(true)
{
simulation.RunIteration();
backgroundWorker.ReportProgress(-1, simulation);
}
}
You should not have to do anything special.
Your ProgressChanged handler can 'unpack' the data and set the relevant properties of controls. Invalidation and repainting is automatic and it runs on the GUI thread.
You should only be careful with updating 'too often'. How often is too often depends on the volume of data, the handler should be finished well before the next update. If not, build in some throttling mechanism.
ProgressBar is the method I recommend. If the data you want to send to the GUI is text then you could have a rich textbox or just a regular textbox and pass text to it when the progress bar is changed:
public void SomeThread_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
/* Update progress bar */
ProgressBar.Value = (e.ProgressPercentage);
if (e.UserState != null)
{
TextBox.Text += (string)e.UserState;
}
}
For other forms of data you could include an If statement which does X when the progress bar is given a certain value.
But ithout knowing more about what you're specifically trying to do I'm afraid I can't provide any more help than that.
Hi
I'm opening a form like this from my main form when the user makes a selection of a menu item.
private void commToolStripMenuItem_Click(object sender, EventArgs e)
{
Command_Form Command_Form1 = new Command_Form();
Command_Form1.ShowDialog();
// Command_Form1.Dispose(); this didn't help
}
Inside the form "Command_Form1"
I close it like this when the user clicks on the close button
private void Close_button_Click(object sender, EventArgs e)
{
this.Close(); //I get the exception here
}
This process works fine once but on the second closing of the form
(Which I hope is a completely different/new instance of the form) I get the error in the title of this post.
This is the output in the debug window.
A first chance exception of type 'System.InvalidOperationException' occurred in System.Windows.Forms.dll
All the topics that list this error go on about not trying to do anything to a form that has not been displayed but this happens when I click on a button in the form.
It would seem to me that pretty much ensures the form has been displayed if I'm able to click its button.
The other posts I've found that list this type of error go on about making thread safe calls so I tried this as an experiment but it didn't make any difference.
private void Close_button_Click(object sender, EventArgs e)
{
if (this.InvokeRequired)
{
CloseCallback d = new CloseCallback(Close_button_Click);
Invoke(d, new object[] { sender, e });
}
else
{
this.Close();
I have multiple threads in my application but they are created by the controls I'm using not by me explicitly.
I am passing data from a serial port to/from the form by Marshling the received/sent data via a delegate[s].
It makes sense that the serial port would run on a different thread than the form but why would a button click on a form be in a diffrent thread than the form????
The whole thread thing is very confuzing
How do I figure out what threads originated where and what is going on in the threads that I didn't create explicitly?
Why would I need to invoke the form's close method via a delegate?
Heck is there anything I can do in this multi threading environment that is thread safe How in do I know if what I'm doing is unsafe/safe if I don't know what/where/why/who/when is creating threads?
My guess is your close() call is not throwing that exception, but something that happens after close(). Have you stepped into the code with the debugger to see when it is fired?
As to when you need to invoke...There is only one thread allowed to make changes and access dynamic properties on the GUI, call it the GUI thread. The GUI thread is responsible for updating layout, firing events like buttons, etc. If you ever access the GUI from another thread (like a timer event) you need to use invoke() to queue your function to be run on the GUI thread. BeginInvoke will also queue the function but is asynchronous (will only queue the function to be run on GUI thread, but will not wait for it to finish).
Close_button_click will only be called by your gui thread when the button click event fires(unless you explicitly call it somewhere else in your code behind, not recommended!), so invokeRequired=false in your code above, and the invoke code is never executed.