I want my C# program to collect data. Then, when the OK button is clicked, I want this data to be loaded into my program -- such as into variables in Main(), or into data members of a class I have constructed, and I want the form to then go away -- not be hidden, but actually closed. Alas, read as I might in the book I have, the data collected by the form stays in the form, execution proceeds within the form, and the same form is used to display the result of the program's computations. Sheesh. All I want is to capture the form's information, close the form and proceed with my program. I would appreciate some tips on geting data from a form into Main() or into a class's data members.
Thanks,
Lucky
What you want to do is perfectly acceptable, it just isn't typical.
When you use Visual Studio to generate a WinForms project, it creates one form for you and
generates a call to Application.Run(new Form1()). For this version of the Run() method, your application will exit when the "main form" (the one passed to Run(), in this case Form1) closes.
There are three overloads (versions) of Application.Run(). For your purposes, you need to use a different overload:
Application.Run(ApplicationContext)
When you use this overload of Run(), you get to control when the application exits. In a nutshell, here's one way you could do it:
Create a class which inherits
ApplicationContext.
In its constructor:
Create your form.
Subscribe to its Closing and Closed events.
Show your form.
In your FormClosing event handler,
get the data from the form.
In your FormClosed event handler, do
whatever you want to do with the
data, and then exit the thread (or do something else).
Here's a crude example, but I will leave out the code for the form itself. Assume the form simply has one TextBox which has its Modifiers property set to Public. (This is NOT an elegant way to get data from a form, but that part is up to you).
namespace Me.MyDemo
{
static class Program
{
[STAThread]
static void Main()
{
MyApplicationContext ac = new MyApplicationContext();
Application.Run(ac);
}
class MyApplicationContext : ApplicationContext
{
string _text = "";
public MyApplicationContext()
{
Form1 f1 = new Form1();
f1.FormClosing += new FormClosingEventHandler(f1_FormClosing);
f1.FormClosed += new FormClosedEventHandler(f1_FormClosed);
Console.WriteLine("I am here. Showing form in 1 second...");
Thread.Sleep(1000);
f1.Show();
}
void f1_FormClosing(object sender, FormClosingEventArgs e)
{
_text = (sender as Form1).textBox1.Text;
}
void f1_FormClosed(object sender, FormClosedEventArgs e)
{
Console.WriteLine("You wrote: " + _text);
Console.WriteLine("I will go away in 2 seconds...");
Thread.Sleep(2000);
ExitThread();
}
}
}
}
Of course, you don't have to exit the thread. You can leave it running if there are other things for your program to do. It will just run as a windowless process. Just remember that you're responsible for eventually ending it.
For more help, look at the documentation for the System.Windows.Forms.Application class, and the ApplicationContext class.
For getting the data from your form, there are many ways to approach this. The simple way is to just give your form some public properties. A more sophisticated way would be to create a data class and use data-bound controls on your form.
You're writing in WinForms? As far as I know a Windows application has to have a window, even if it's one pixel by one pixel.
Have you seen any other Windows applications that work the way that you want yours to work? Opens a window, the window closes, but the program keeps on running? This is generally considered undesired behavior, similar to viruses and trojans.
You can create a console application or a Windows service with no GUI, of course.
What is the application doing behind the scenes after the data is entered? If it's just doing some calculations and saving to disk, uploading, or printing, leave the window open for that and then exit when it's done. Possibly include a progress bar.
Related
Hello Everyone
In the following, I am going to give you a routh idea of what I am trying to accomplish with the program I am trying to code at the moment bevor describing the problem I am struggeling to solve. Thanks for your help!
The Program
Purpose
Timers. Multiple of them. Each timer should be displayed on an individual form, being controlled by individual buttons and having a unique design, once again set up by user settings.
Layout
The program itself should be made up by one main form, containing all "start" and "stop" buttons for each timer. However, the timer forms should be open at all time. Meaning, once the user has changed the properties, all timer forms should be closed again and depending on the settings new forms should open.
Question
In generell, I know how to open a form in such a way to change properties and componants from another form. Example:
namespace example
{
public partial class Form1 : Form
{
Form2 timerForm1;
private void Form1_Load(object sender, EventArgs e)
{
timerForm1 = new Form();
timerForm1.Show();
}
//now you are able to access Form2 in different functions, like:
{
timerForm1.label1.Text = "00:02:56";
}
}
}
However, I need to open as many forms as the user declares, meaning I can not set up variables in fore hand. However, I need to access those opend forms just like in the given example.
I would like to store the different, user declared timers inside an array or list if possible, if there is a smarter, easier or faster way i can adapt and change it to whatever is required to get it working.
I didn't really understand what or if you have an issue with the timers. But controlling various amount of forms from each individual is not that hard.
As I understand that you want to control various amount of Form2 instances from one Form1. In that case you can make a List of Form2 and add each Form2 you creat to that list.
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;
}
So I've got some serious problems with removing a Control from a Form of my application. It's kinda messed up but I can't change anything. I have a form and I have a separated user Control. The control opens an exe file and shows a progress bar while loading it's bytes. And here comes the problem. I do all of it with a BackgroundWorker and when the worker_DoWorkerCompleted method is called the original form should show a MessageBox and remove the Control.
BackGround_Loader bgLoad = new BackGround_Loader();
bgLoad.Location = new Point(this.Width/2 - bgLoad.Width/2, this.Height/2 - bgLoad.Height/2);
this.Controls.Add(bgLoad);
bgLoad.BringToFront();
bgLoad.AddReferences(this.executableFile, this.SourceReader);
bgLoad.occuredEvent();
At first I set the control's location to be in the middle of the Form itself. Then I add the control to the form, and bring it to the front. After these I send the path of the executable and a RichTextBox's reference to this. With the occuredEvent I start the BackgroundWorker itself. And here comes my problem. I should show a MessageBox in the Form when the in the bgLoad the backgroundworker gets to the DoWorkerCompleted status. Kindly I have no idea how to do it. It works just perfect however the control stays in the middle of the form.
UI actions must be performed on the main UI thread. The events that get raised from the background worker thread are (obviously) in a different thread.
You need something like the following code:
private void backgroundWorker_DoWork(object sender, AlbumInfoEventArgs e)
{
// Check with an element on the form whether this is a cross thread call
if (dataGridView.InvokeRequired)
{
dataGridView.Invoke((MethodInvoker)delegate { AddToGrid(e.AlbumInfo); });
}
else
{
AddToGrid(e.AlbumInfo);
}
}
In this case AddToGrid is my method for adding a row to a DataGridView, but in your case it will be a method that does what you need to do.
Similarly for the backgroundWorker_RunWorkerCompleted method
See this MSDN example
I could find a way to solve the problem but I don't really like it. In the addReferences method I pass the Form itself and an object of the bgLoad class. Then in the RunWorkerCompleted I check if the control is on the form and if it is then I remove it.
bgLoad.AddReferences(this, bgLoad, this.executableFile, this.SourceReader);
...
private void worker_DoWorkerCompleted(object sender, DoWorkerEventArgs e) {
if(this.MainForm.Controls.Contains(this.Control) {
this.MainForm.Controls.Remove(this.Control);
}
}
Like this it works but it's awful for me.
Short version: I want to trigger the Form_Load() event without making the form visible. This doesn't work because Show() ignores the current value of the Visible property:
tasksForm.Visible = false;
tasksForm.Show();
Long version: I have a WinForms application with two forms: main and tasks. The main form is always displayed. The user can either click a button to open the tasks form, or click some buttons that just run a task directly without opening the tasks form.
When a user asks to run a task directly, I'd like to just call some public methods on the tasks form without showing it. Unfortunately, the task logic depends on stuff that happens in the Form_Load() event. The only way I can find to trigger Form_Load() is to call Show(). The best I've been able to do is to show the form in the minimized state:
tasksForm.WindowState = FormWindowState.Minimized;
tasksForm.Show();
I suppose the cleanest solution would be to pull the tasks logic out of the tasks form and into a controller class. Then I can use that class from the main form and from the tasks form, and only load the tasks form when I need it visible for the user. However, if it's an easy thing to load the form without displaying it, that would be a smaller change.
Perhaps it should be noted here that you can cause the form's window to be created without showing the form. I think there could be legitimate situations for wanting to do this.
Anyway, good design or not, you can do that like this:
MyForm f = new MyForm();
IntPtr dummy = f.Handle; // forces the form Control to be created
I don't think this will cause Form_Load() to be called, but you will be able to call f.Invoke() at this point (which is what I was trying to do when I stumbled upon this SO question).
It sounds to me like you need to sit down and re-think your approach here. I cannot imagine a single reason your public methods need to be in a form if you are not going to show it. Just make a new class.
I totally agree with Rich B, you need to look at where you are placing your application logic rather than trying to cludge the WinForms mechanisms. All of those operations and data that your Tasks form is exposing should really be in a separate class say some kind of Application Controller or something held by your main form and then used by your tasks form to read and display data when needed but doesn't need a form to be instantiated to exist.
It probably seems a pain to rework it, but you'll be improving the structure of the app and making it more maintainable etc.
From MSDN:
Form.Load
Occurs before a form is displayed for the first time.
Meaning the only thing that would cause the form to load, is when it is displayed.
Form.Show(); and Form.Visible = true; are the exact same thing. Basically, behind the scenes, Show checks for various conditions, then sets Visible to true. So obviously, setting visible to false (which it already is) before showing the form is meaningless.
But let's forget the technicalities. I completely agree with Rich B and Shaun Austin - the logic shouldn't be in that form anyway.
Sometimes this would be useful without it being bad design. Sometimes it could be the start of a migration from native to managed.
If you were migrating a c++ app to .NET for example, you may simply make yourwhole app a child window of the .NET form or panel, and gradually migrate over to the .NET by getting rid of your c++ app menu, status bar, toolbar and mapping teh .NEt ones to your app using platform invoke etc...
Your C++ app may take a while to load, but the .NET form doesn't..in which you may like to hide the .NEt form until your c++ app has initialised itself.
I'd set opacity=0 and visible=false to false after calling show, then when your c++ app loads, then reverse.
If you make the method public, then you could access it directly.... however, there could be some unexpected side effects when you call it. But making it public and calling it directly will not draw the screen or open the form.
Move mandatory initialization code for the form class out of the Load event handler into the constructor. For a Form class, instantiation of an instance (via the constructor), form loading and form visibility are three different things, and don't need to happen at the same time (although they do obviously need to happen in that order).
None of the answers solved the original question, so, add the below, call .Show() to load the form without showing it, then call .ShowForm() to allow it to be visible if you want to after:
private volatile bool _formVisible;
protected override void SetVisibleCore(bool value)
{
base.SetVisibleCore(_formVisible);
}
public void ShowForm()
{
_formVisible = true;
if (InvokeRequired)
{
Invoke((Action) Show);
}
else
{
Show();
}
}