I was working on a software in Visual Studio, writing code in C#, while I noticed something. I can't figure out how to exit the application.
namespace WindowsFormsApp2
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void ExitButton_Click(object sender, EventArgs e)
{
Application.Exit(); // This works, when I run the application and click on the button, it will indeed quit.
}
}
}
So as said, when I click on the button, it will indeed quit the application. However if I place Application.Exit(); somewhere else, it won't work. So if I modify Form1() like this, it won't automatically quit the application:
public Form1()
{
InitializeComponent();
Application.Exit();
}
It would be necessary to quit the application instantly if certain conditions are met, for example if some application files are missing.
I than tried to do the following:
namespace WindowsFormsApp2
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
closeapp();
}
public void closeapp()
{
Application.Exit();
}
private void ExitButton_Click(object sender, EventArgs e)
{
closeapp();
}
}
}
Now if I run the application, it will not exit automatically, however, if I click on the Exit button, it will quit the application.
So it looks like that if it is not called from a event that happens within the form, it will not close the application.
I have searched online (including Google and StackOverflow) with the keyword "Application.Exit();" not working. They recommended that I use "Environment.Exit();". Now in my testing application, this works, but in the real application that I am working on, when I remove all the code (of course while having a backup), it looks like the following and it still does not work.
namespace Censored
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
Environment.Exit(1);
}
}
}
What can possibly be the cause of it not working in one application, but working in another one? Is something corrupted?
You can't apply Application.Exit when the application is being initialized. So, why don't you force to exit the application in the FormLoad if your conditions aren't met;
private void Form1_Load(object sender, EventArgs e)
{
Application.Exit();
}
I think the best thing to do here is not Application.Exit because as you said, you want to quit the application because there are some files missing. If there are indeed some files missing, you should really show a message to the user and then quit. Application.Exit will quit the application silently so the user does not know that some files are missing. Bad UX!
One easy way to show an error message is to throw an exception:
throw new FileNotFoundException(
"Some application files are missing! Please add them in before starting this application!");
The reason why Application.Exit does not work here is because the "Application" has not been created at that point in time. In your Main method, you should have this line:
Application.Run(new Form1());
The "Application" will be created after the above method is called. But before Run is called, what else is called? The form's constructor! It then calls InitializeComponent, where you want to exit the application. At this time Run has not been called yet!
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I currently have 3 forms, a main menu, form 2 and form 3. Is there an optimised way of opening forms (and closing them) as when I switch between them they are taking memory up and I can quickly get to a few GBs usage switching between them over a few minutes.
private void button2_Click(object sender, EventArgs e)
{
this.Hide();
NewForm NewForm = new NewForm();
NewForm.ShowDialog();
this.Close();
this.Dispose();
I've found if comment out this.Hide() my forms aren't actually closing. How can I close the forms when the new one is opened?
Presumably, you're using ShowDialog() to keep the app from exiting when the original, main form is closed?
A different approach would be to use the overload of Application.Run that receives an ApplicationContext.
Then you could write your own "application context" and tell the application to only exit when there are no more forms open. This will allow you to switch from ShowDialog() to Show(). The small change means the old form will be disposed of since code execution continues after Show().
Back in our ApplicationContext class, we can wire up the Idle event and check the count of open forms in Application.OpenForms, letting us know when all forms have been closed and it is time to shut down the application.
So your "program.cs", would change to:
static class Program
{
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new MyAppContext(new Form1()));
}
}
public class MyAppContext : ApplicationContext
{
public MyAppContext(Form startingForm)
{
startingForm.Show();
Application.Idle += Application_Idle;
}
private void Application_Idle(object sender, EventArgs e)
{
if (Application.OpenForms.Count == 0)
{
Application.Exit();
}
}
}
Now, whenever you want to switch forms, just make sure to Show() the new form before you Dispose() of the current one:
private void button1_Click(object sender, EventArgs e)
{
Form2 f2 = new Form2();
f2.Show(); // make sure you "Show()" the new form BEFORE disposing of the current one below
this.Dispose(); // dispose of the current form
}
With all that in place, the application will shut down automatically once the last form is closed, and the old forms should get disposed of properly.
Remember, though, that the GC manages memory for you...and it might decide that it is going to hold on to that memory to make things load faster in the future. This approach simply addresses the problem that the Dispose() call wasn't being hit since ShowDialog() was stopping execution.
This is baffling me. When clicking the button in the windows form project, the code below results in 'Exception thrown: 'System.EntryPointNotFoundException' in mscorlib.dll'. I cannot figure out why. The app doesn't crash, and the task (or any amount of tasks) continues just fine, with everything working as it should.
What's going on here?
namespace FormsExperiment
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void btn_fire_Click(object sender, EventArgs e)
{
Task.Run(() => "Hello");
}
}
}
Edit: Trying this on another computer, I'm not able to reproduce the bug. I'm going to chalk this up to VS2015 weirdness that seems beyond the scope of stackoverflow. Thanks for the replies all - the code here works, the error just makes no sense.
I have developed a program for Windows 7 and it runs on my computer as it should (in release mode). However, when I copy and paste the project folder to my external HDD and try it on a different computer, it 'runs' but nothing really shows up. I will try to post relevant code:
class App : Application
{
[STAThread()]
static void Main()
{
new App();
}
/// <summary>
/// Starts application with splash screen
/// </summary>
public App()
{
StartupUri = new System.Uri("SplashScreen.xaml", UriKind.Relative);
Run();
}
}
Even though this screen is never visible, my MessageBox is shown.
//constructor
public SplashScreen()
{
//generated method
InitializeComponent();
System.Windows.MessageBox.Show("WHY ME??");
mw = new MainWindow();
mw.Show();
}
After the splash screen, the main window should open, but it doesn't AND this MessageBox never shows up.
public MainWindow()
{
//Windows generated
InitializeComponent();
System.Windows.MessageBox.Show("WHY ME??");
}
As I mentioned, the program runs as it is supposed to in both release and debug mode, but then when I bring it to another computer it only shows "WHY ME??" once instead of twice like it should. Any ideas?
Turns out there was a lot wrong with my code. One of the largest problems I had was hard-coded file paths to the computer it was running on. However, what really helped me with all computer-migration related problems was adding the following code to each class:
In Constructor:
AppDomain.CurrentDomain.UnhandledException += CurrentDomain_UnhandledException;
Create handling function:
void CurrentDomain_UnhandledException(object sender, UnhandledExceptionEventArgs e)
{
System.Windows.MessageBox.Show(e.ExceptionObject.ToString());
}
It is slow and tetious however it does a pretty good job of assisting in locating source of problems. So there was multiple things wrong with my program, but adding the above code helped solve a lot of issues.
I'm just trying to learn this thing and in future, wanted to use it in one of my projects.
I have a small Form with a simple Text box, stored in a .Net dll (C#). And here is my class in this dll which contains methods to interact with this Form:
using System;
using System.Collections.Generic;
using System.Text;
namespace ClassLibrary1
{
public class Class1
{
static Form1 dlg = new Form1();
public static void ShowForm()
{
dlg.ShowIcon = true;
dlg.Show();
}
public static void SetText(string MyText)
{
dlg.Text = "Form Text ";
dlg.SetText(MyText);
}
}
}
Successfully loaded this form by referencing this dll into another C# application while calling its method i.e.:
private void button1_Click(object sender, EventArgs e)
{
ClassLibrary1.Class1.ShowForm();
}
And I was able to interact with the form perfectly.
Now loading same in Powershell using:
[Reflection.Assembly]::LoadFile("D:\Playing\ClassLibrary1\ClassLibrary1\bin\Debug\ClassLibrary1.dll")
[ClassLibrary1.Class1]::ShowForm()
Now this is loaded successfully at its default position, but I can't interact with this form i.e. I can't type in its Text Box, neither I can move or even close this form by clicking on its Close (x) button on right corner. Whenever I put my mouse on it, it becomes a HourGlass i.e. waiting for some process .
To verify if form is not hanged, I called SetText at Powershell prompt:
[ClassLibrary1.Class1]::SetText("String from Powershell")
and it worked fine. TextBox received this text properly, but still I can't interact with the form with my mouse.
I feel, I have to manually set its Window Handler i.e. System.Windows.Forms.IWin32Window.
But I don't know which Handler and how to achieve this?
Please guide .... Would really appreciate for any alternative tricks.
You can't show a form from PowerShell using Form.Show() method because it needs a message pump (and it's not provided by PowerShell host process).
Here what you can do to solve this issue:
Use Form.ShowDialog() or Application.Run(), your form will have its own message pump.
It'll be modal then you need to run it in another thread. I suggest to use a background thread and BeginInvoke() in your SetText() method.
Here code to do that (I won't change your code too much so I'll keep it as a singleton instance even if this prevents to display form multiple times). Code is just an example (I wouldn't suggest to use Thread Pool for this task) to illustrate the procedure.
public static void ShowForm()
{
if (dlg != null)
dlg.BeginInvoke(new MethodInvoker(delegate { dlg.Dispose(); }));
ThreadPool.QueueUserWorkItem(delegate(object state)
{
Application.Run(_dlg = new Form1());
});
}
public static void SetText(string text)
{
_dlg.BeginInvoke(new MethodInvoker(delegate { dlg.SetText(text); }));
}
In this way Form1 will be modal in another thread (with its own message pump) and your calling PowerShell thread won't be stopped. Communication between them is still possible via message dispatching (Invoke()/BeginInvoke()).
Please note that SetText() is now asynchronous, to make it synchronous just replace BeginInvoke() with Invoke().
I've got an application what's working with two video streams.
When the form is being closed, it runs this function:
private void Form1_FormClosed(object sender, FormClosedEventArgs e)
{
if (FinalVideoDevice.IsRunning) { FinalVideoDevice.Stop(); }
if (streamMJPEG.IsRunning) { streamMJPEG.Stop(); }
Application.Exit();
}
But in reality it doesn't kill the application, only hides the form, but still is seen from TaskManager/Processes.
Any ideas what I might be doing wrong?
Thanks!
Assuming you are in Windows Forms you can call Application.ExitThread();
in general one of the reasons why you still see the process in TaskManager could be that you still have some background / worker threads active.
Roger check this question/answers as well: Application.Exit