I have an odd question which I haven't been able to find a solution to.
Basically, I have a console application. It takes commands, which I determine actions from. All of the actions involve opening a form and displaying something.
Currently, I'm able to enter a command, it correctly determines the action and pops up a form and everything is okay.
Unfortunately, in doing so, the console in the background behind the form essentially freezes (I've realised it just isn't updating the UI anymore) - so if I try and type another command while there's a form open, nothing will happen until I close the form.
I've been looking into creating a new thread for the form to run in which I guess is the path I need to take - but I can't figure out how to do that while not causing errors (e.g. that pesky illegal access from a separate thread error).
Can anyone help?
Should I cave and just set up a form from the get-go and make my commands be entered via a textbox on a form? (seems annoying, but at least I then have a form that can invoke other things)
You can open forms from a console application in another thread like this:
var t = new Thread(() => {
var f = new Form();
f.ShowDialog();
});
t.SetApartmentState(ApartmentState.STA);
t.Start();
Related
I have a very simple GUI application in C# and there is some codes in Form Load function. I just want to start and close the application without showing Form for running those codes in form load function.
How to do it?
If you don't want to show a form, you should move your code to the Main() method and get rid of the form.
Or you could try to create a service which contains no GUIs
http://msdn.microsoft.com/en-us/library/zt39148a%28v=vs.110%29.aspx
form.Opacity = 0;
I am not sure if this is what you want.
EDIT: - This will keep form opaque and you can run and close it when an event occur.
I'm working on a console application that creates a form to alert users of some given state - at a later stage, the code base will become a class library.
For now, however, I need to show the form (ShowDialog would be the best method here, I guess) THEN call an arbitrary method before the form closes.
As an example, I need to show the form, set the text value of a label control, wait for n number of seconds, then change the value of the label, then close the form. I know that this sounds a little trivial, but I'm trying to proof-of-concept the design.
I've taken a look around and it doesn't look like this is possible, as ShowDialog() requires me to close the form before I can continue through code listing in the calling method/class.
Here's what I have so far:
PopUpForm myForm = new PopUpForm(string messageToDisplay);
myForm.ShowDialog();
//call myForm.someMethod() here, before the form closes
//dispose of the form, now that we've no use for it
myform.Dispose();
//target method in PopUpform class
public void someMethod()
{
lblText.Text = "Waiting for some reason";
//wait n number of seconds
lblText.Text = "Finished waiting. Form will now close";
//it doesn't matter if the form closes before the user can see this.
}
It looks like ShowDialog() doesn't support this sort of behaviour. I'm looking into BackgroundWorker threads, but was wondering if anyone has any advice on this, or have encountered this before.
If you want to show the form, then continue working, then close it - you can do so via Form.Show() instead of Form.ShowDialog():
using (var myForm = new PopUpForm(messageToDisplay))
{
myForm.Show(); // Show the form
DoWork(); // Do your work...
myForm.Close(); // Close it when you're done...
}
However, if this is purely a console application (and doesn't have a message pump), then this will likely not work properly.
Other options would be to provide a timer within your Form to have it close, or pass a delegate into the Form to run your method on Show, after which it could close itself.
at a later stage, the code base will become a class library.
When you do this, you'll likely want to come up with a different mechanism to provide notifications. Coupling your library to a specific UI technology is a bad idea. It would likely be better to have your library just provide events or other notification, and allow the user to provide the UI/notification to the user.
If this code ie destiend to end up in a code library, I recommend against having it display any forms, ever, of its own volition. The library should generate events, or in some cases exceptions, that can be caught by the invoking application to allow it to display the form. If certain details requiring presentation to the user are internal to the library, expose a DisplayEventData() method from the library.
The ShowDialog-method creates a "modal" window, and usually blocks the UI until you close it (either by clicking OK or Cancel). You would need to create a WinForm yourself, can be a simple one though and create a message-pump for it. You can run your own form by calling
Application.Run(YourForm);
You would need to hold your console-thread with a mutex for example, to keep it from continuing, while the form is open.
The form offers all the methods you know from WinForms like Close, where you could tell your console-thread to continue.
See this on MSDN.
I am trying to create a simple c# application (my first attempt at c# so please be kind). I've created a form with a textbox to capture an "auth code", which is then validated and then a webclient fetches an xml file passing this auth code in to the request. The data sent back is parsed e.c.t.
What i want to do is once the xml comes back and ive done my checks to valid it is all fine. I want to close the first form and load up a second form where i will programmatically add the form components needed to display the xml data in a pretty format.
My problem is that im unable to get the second form to stay open (im no doubt invoking the second form in the wrong manner). Here's what i have:
// close current form
this.Close();
//open new form
xmlViewForm xmlView = new xmlViewForm();
xmlView.Show();
I'm sure you've spotted the mistake im making by now. but just to state the obvious for the sake of completeness, it closes the first form, opens the second, and then immediately the program exits (the second form flashes up for a second obviously).
I've tried a few things but none of them work (including using Application.Run(new xmlViewForm()); instead of instantiating the class and using the show() method. Obviously you know that doesn't work, and now i do too, although i dont understand c# even remotely enough to work out why.
Thanks for any help :)
The first thing that came to mind is that you are closing the form that you opened by calling Application.Run(new MyForm()) or something similar. This form has special significance; it is the "main form" of the application, and when closed, it signals to the application that the user wants to close the entire program, no matter how many other windows are open.
There are two possible fixes. First, and easiest, is simply to Hide() the form you don't want visible instead of calling Close() on it. Though invisible, it's still running, so the application doesn't close.
The second solution is to define a custom "application context" that should be run instead of the "default context" that is created by specifying a main form to watch. You do this by deriving a custom class from System.Windows.Forms.ApplicationContext. With this context specified, you can use it to control termination of the application based on something other than closure of the main form. Example code that launches two "main forms" and keeps track of whether both are still active can be found at the MSDN page for the class. You can do something similar by specifying Load and Close handlers for the main form, then passing them to the child form when the main form instantiates it, thus keeping a count of "open" forms, and closing out the full application when that number is zero. Just make sure the child form loads before closing the main form by calling childForm.Show() before this.Close().
You can not open the second form after closing the main form.
Do this:
//open new form
xmlViewForm xmlView = new xmlViewForm();
xmlView.Show();
// hide current form
this.Hide();
Main form can not be closed because it's the parent form. The child form will never show up if you close the main form.
Or change the xmlViewForm to main form by editing Program.cs file
Application.Run(new XmlViewForm());
Then you can easily call the other form first at the time of loading and close it as you please:
private void XmlViewForm_Load(o, s)
{
// hide current form, and this will remain hidden until the other form is done with it's work
this.Hide();
//open the other form
TheOtherForm _theOtherForm = new TheOtherForm();
_theOtherForm.Show();
}
private void TheOtherForm_Closed(o, s)
{
// show current form
this.Show;
}
I have an older form that I really don't want to rewrite at this point, so what I'm doing is loading the form and then adding it to a panel in the new UI form. This is working fine, but it's slow. The old form does a lot of loading and gathering of data and it's not very efficient. So as a result larger records take up to 30 seconds to load. As you know, creating the form then "locks up" the main UI for about 30 seconds while it loads the old form. This is the action I'm trying to prevent. I want to load the new form, display a "Loading" gif in the blank panel, and then once the old form is loaded remove the "Loading" image and add the form as a control.
And here starts the problem.
I've tried creating a Background Worker but this causes a STA error (old form has a few threaded data loadings of it's own), and since I can't change the worker to STA I stopped trying.
I've tried to create an Invoke (and BeginInvoke) and while this works, it doesn't really load the old form in the thread. It simply sends it back to the UI thread and does the work there. Again this hangs the UI. I.E.: Not what I want.
I've tried to create a delegate and trigger it as an event in the thread, but I get the same results as below...
I've created a thread, set STA on it, started it and then did a while loop with a DoEvents waiting on it to finish. Of course this all seems to work up to the point of accually adding the form to the panel, and then I get the "Control 'ChartForm' accesses from a thread other than the thread it was created on". In this error 'ChartForm' is the old chart that was loaded in the thread.
I've tried the above method, but I instead used a private static field to hold the creating of the old form, and then adding it to the panel once the thread is completed. This is in the method that created the thread, just after the while loop. Same error.
So, I've used the above method in other places with DataTables and didn't have any issue getting the data back to the main thread for use with DataBinding. I know that this is a little different but I didn't think that it would be this hard to do.
Below is the code that I have tried to use that seems to be the closest to what I want.
private static _ChartForm;
private void LoadPatientChart()
{
ClearMainPanel(); // Removes any loaded ChartForms from Panel
if (_Patient == null) // Test to make sure a patient is loaded
return;
loadingPanel.Visible = true; // Displays the "Loading" gif
Thread thread = new Thread(new ThreadStart(this.GetChartForm));
thread.SetApartmentState(ApartmentState.STA);
thread.Start();
while (thread.ThreadState != ThreadState.Stopped)
Application.DoEvents(); // Keeps the UI active and waits for the form to load
this.ChartPanel.Controls.Add(_ChartForm); // This is where the error is
loadingPanel.Visible = false; // Hide the "Loading" gif
}
private void GetChartForm()
{
ChartForm chartForm = new ChartForm(_Patient.AcctNum.ToString(), false);
chartForm.TopLevel = false;
chartForm.FormBorderStyle = FormBorderStyle.None;
chartForm.Dock = DockStyle.Fill;
chartForm.Visible = true;
_ChartForm = chartForm;
}
It's really not a good idea to create UI controls on any other thread than the UI thread. It is technically possible, but it's difficult to manage, especially if the new thread is a "temporary" one.
What you really need to do is refactor out the work that the ChartForm is doing (on construction it appears?) and do that work on a background thread, and then return it to your UI thread and then create your ChartForm passing in the results of that work. IMHO this is a better design anyways; although it may be a lot of work for you.
I don't think what you want is possible without refactoring this "old form". There is only one UI thread, and all UI elements must be created on that thread to be displayed to the user.
I would suggest refactoring the form to display initially without any data (or maybe with a loading image), and then have the form start a background task using BackgroundWorker to perform the long running tasks that are not UI related (going to a database, etc.) Once the worker is complete, then you can run the code that initializes the Form's data elements. This will keep the UI responsive for as long as possible while the blocking tasks are performed.
I've tried to create an Invoke (and BeginInvoke) and while this works,
it doesn't really load the old form in the thread. It simply sends it
back to the UI thread and does the work there. Again this hangs the
UI. I.E.: Not what I want.
You must update the user interface on the main thread, you do not have any choice, if its still hanging then your doing the calculations in the wrong thread.
I'm having some serious issues with a WinForm application that I'm working on.
Currently, I'm using Form1.ShowDialog(); to display a form. This code is contained in a background worker that looks for changes in a database. Using Form1.ShowDialog(); only allows 1 form to open at a time, even if there are multiple changes to the database. What I want to have happen is for multiple forms to open at once if there is more than one change in my database.
When I use Form1.Show();, the application blows up. For some reason, the Show() method makes the forms not display properly (all the elements in the form are missing).
Is there anything I can do to make my code work the way I want it to?
Edit: here's a code snippet
//result is a linq result
foreach (var row in result)
{
Form1 Form = new Form1();
Form.ShowDialog();
}
After a first look, I can tell you this:
Showdialog can't work the way you intend: this very method makes the owner inactive until the dialog is closed. In your case, the loop will pause at the first showdialog, then resume when you close the form, opening a new one and so on until the loop is finished.
As for the "show" problem, creating empty forms, I need more information. The rest of the code and the exception(s) you're getting.
Two points from the top of my head:
1) To open more then one form , use non modal (modeless) method (i think
the show() method). see for example http://msdn.microsoft.com/en-us/library/39wcs2dh.aspx
2) I am not sure you can call UI related method from a non UI thread. You might want to send an event to your UI thread from the worker thread and the UI thread will call the show method