I'm trying to figure out how when simply showing a WinForms dialog (code below) I get the following Exception and callstack. This doesn't happen all the time, but I'm seeing it in my exception logs. Any ideas? I can't figure out what would be referencing a disposed object?
I've verified (via the rest of the callstack) that the application is not shutting down, it is running normally.
System.ObjectDisposedException: Cannot access a disposed object.
Object name: 'MainForm'.
at System.Windows.Forms.Control.CreateHandle()
at System.Windows.Forms.Form.CreateHandle()
at System.Windows.Forms.Control.get_Handle()
at System.Windows.Forms.Control.GetSafeHandle(IWin32Window window)
at System.Windows.Forms.Form.ShowDialog(IWin32Window owner)
at MyApp.MainForm.PromptForProfile()
at MyApp.MainForm.LoadProfile()
at MyApp.MainForm.barButtonItem1_ItemClick(Object sender, ItemClickEventArgs e)
This is the code for the dialog being displayed. The only "goofy" code is probably the textPassword_KeyDown handler. I should probably pull the code I want out and not call btnOK_Click that way.
public partial class ProfileForm : DevExpress.XtraEditors.XtraForm
{
public string _username;
public string _password;
public ProfileForm()
{
InitializeComponent();
}
private void btnOK_Click( object sender, EventArgs e )
{
_username = textUsername.Text;
_password = textPassword.Text;
}
private void textPassword_KeyDown( object sender, KeyEventArgs e )
{
if ( e.KeyCode == Keys.Enter )
{
btnOK_Click( sender, null );
this.DialogResult = DialogResult.OK;
e.Handled = true;
}
}
private void hyperLinkEdit1_Click( object sender, EventArgs e )
{
// show the proxy settings dialog
ProxyForm pform = new ProxyForm();
pform.ShowDialog();
}
}
Well, one possibilily is that you're setting DialogResult to Ok, which will close the form, but you then refer to the eventarg triggered by pressing Enter.
I'm not too sure of the role of the hyperlink edit1 bit, though. Is it on the same form, or a calling form?
Your stack trace tells me that you aren't getting into the ProfileForm code. It's failing on some control's CreateHandle. Without more information, I can only guess:
Verify that you're performing all your UI manipulation is occurring on your GUI thread. Even if you think it is, double check. (Sometimes the threading can be subtle.)
Make sure that you aren't trying to display the same form instance twice, the second time after it's already been disposed. I see that you've got a ShowDialog() happening, but if you're trying to ShowDialog() on a form that's already been disposed, I'd expect it to explode like this.
Ensure that any usercontrols on the form behave properly.
Consider using a secure string for your password field.
Related
I have a form with a full picture which helps players to see where to move their puzzles in the game. When I show it for the second time, after I closed it, System.ObjectDisposedException is thrown.
I tried to use Hide() method when FormClosed event happened but it did not help. Also, I deleted the pictureBox from the control because I thought that it was causing this exception but is did not help either.
Original_px OrPix = new Original_px();
private void showFullPictureToolStripMenuItem_Click(object sender, EventArgs e)
{
OrPix.Show();
}
I want this form to work without this exception
If you close the form, through the close upper right icon or through code calling the form Close() method then the variable OrPix will reference a closed and disposed object.
You cannot reuse it without reinitilizing the variable with new Original_px();.
You need to know when the form is closed and you can receive this information handling the FormClosed event and set that variable to null.
So, when you need to display it again (or for the first time) you should check to see if the variable is null and reinitialize it
Original_px OrPix = null;
private void showFullPictureToolStripMenuItem_Click(object sender, EventArgs e)
{
if(OrPix == null)
{
OrPix = new Original_px();
OrPix.FormClosed += PixClosed;
}
OrPix.Show();
}
private void PixClosed(object sender, FormClosedEventArgs e)
{
OrPix = null;
}
Hi I'm relatively new to C# and completely new to windows form and basically trying to create a subliminal messaging program that at timed intervals will quickly display a message for it to then be hidden again.
I've managed to by looking through various other posts created another form that will pop up and then hide very quickly using
msgObject.Activate();
that brings the form to the front. However it is stopping me from being able to type when I'm working and I basically wanting to know if it is possible to make some kind of message or form appear at the front of all my other programs without it interrupting my current work or opening or closing of other windows and tasks if that makes sense. As currently it brings the form to the front of everything but will also stop me from being able to type etc.
I'm not sure if this is possible with my current method of using a form but if there is a way of achieving the result I'm after I'd be very grateful to find out
Thanks.
Here is more of my code to clarify
public partial class FormHomePage : Form
{
private bool startSubliminal = false;
msg msgObject = new msg();
List<string> subliminalMessages = new List<string>();
public FormHomePage()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
}
private void timer1_Tick(object sender, EventArgs e)
{
if (startSubliminal)
{
msgObject.Show();
msgObject.BringToFront();
msgObject.Activate();
}
}
private void button1_Click(object sender, EventArgs e)
{
subliminalMessages.Add(txtBox1.Text);
msgObject.LabelText = txtBox1.Text;
txtBox1.Text = string.Empty;
startSubliminal = true;
msgObject.Show();
msgObject.BringToFront();
}
private void timer2_Tick(object sender, EventArgs e)
{
msgObject.Hide();
}
}
How are you showing the second form (the message form) in the first place? You're probably using .Show() (right?), which will make the form "steal" the focus anyway. The same applies to .Activate() and .BringToFront().
Instead, what you can do is to show the message form and make sure it stays on top the current form, and then activate the current/main form once again.
Something like this should work:
var frm = new YourMsgForm();
frm.Show(this);
this.Activate();
Here's a demonstration:
Note that I used .Show(this) instead of .Show(), that's in order to set the current form as the Owner of the new one, that way we guarantee that the new form will stay on top of the current one. This is equivalent to calling frm.Owner = this; then frm.Show();.
Another way to make sure the form stays on top is by setting the TopMost property instead of the Owner property. However, doing so will make the new form on top of the other windows as well (not just your application).
I'm building a GUI application with C# and gtk#. I've encountered an issue recently and was looking for the best solution to this problem:
I have a modal window that pops up for the user to enter a number. This window is a separate window accessed from my main window and it's set up like this:
public class MainWindow()
{
public NumberEntry numEntry;
Whenever I need numerical input from the user, I call ShowAll() on the public Window property of NumberEntry like:
numEntry.win.ShowAll();
And all of this works fine. Afterwards, to get the value they entered, I call:
int entered = numEntry.valueEntered;
The issue is obviously that code continues executing immediately after the ShowAll() line is finished, and numEntry.valueEntered is always 0. What I'd like to do (and have been trying to do), is to suspend the main thread, and open up the number entry window in a second thread, and join back to the main thread when this is complete. Suspending the main thread seems to prevent GUI changes making the program freeze when I try to open the number entry window. I'd also like to avoid callback methods if at all possible, seeing as how this would get rather complicated after awhile. Any advice? Thanks!
Seems like when GTK window is closed all its child controls are cleared. So to get the result from the custom dialog window you may do the following (I am not gtk guru but its works for me):
1. Create a new dialog window with your controls (I used Xamarin studio). Add result properties, OK and Cancel handlers and override OnDeleteEvent method:
public partial class MyDialog : Gtk.Dialog
{
public string Results {
get;
private set;
}
public MyDialog ()
{
this.Build ();
}
protected override bool OnDeleteEvent (Gdk.Event evnt)
{
Results = entry2.Text; // if user pressed on X button..
return base.OnDeleteEvent (evnt);
}
protected void OnButtonOkClicked (object sender, EventArgs e)
{
Results = entry2.Text;
Destroy ();
}
protected void OnButtonCancelClicked (object sender, EventArgs e)
{
Results = string.Empty;
Destroy ();
}
}
2. In your main window create a dialog object and attach to its Destroyed event your event handler:
protected void OnButtonClicked (object sender, EventArgs e)
{
var dialog = new MyDialog ();
dialog.Destroyed += HandleClose;
}
3. Get the results when dialog is closed:
void HandleClose (object sender, EventArgs e)
{
var dialog = sender as MyDialog;
var textResult = dialog.Results;
}
If you whant you also may specify a dialog result property and etс.
I have a countdown Timer form - on the first form the user will enter the countdown time - warning times, end message, etc. There are also two Radio buttons (Max/Min) and depending on which is selected they will open a new Max or Min form where the time will actually start to countdown. It is working fine and counting down as I expect. However, if I exit the Max or Min form and try to run again with new times I get the error. The code is below - note the comment out ShowDialog(this); was something I tried - it let me close and open the new forms ok but it did not actually start the countdown. UpdateLabels is the function that does the updating of Labels.
bool Max = rbMax.Checked;
if (Max == true)
{
//_Max.ShowDialog(this);
_Max.Show();
}
else
//_Min.ShowDialog(this);
_Min.Show();
UpdateLabels();
}
I also tried the following which I read online as a possible solution but it also did not work...
private void Max_FormClosing(object sender, FormClosingEventArgs e)
{
this.Hide();
this.Parent = null;
}
Can anyone help me out - I can post the UpdateLabels function if needed. I am pretty new to UI C# development so any help would be great. Thanks.
The problem is, that a closed form can not be used anymore (be reopened). Thats why the code you posted tries to stop closing and only hides your window. But for doing this, the Cancel-property must be set to true:
private void Max_FormClosing(object sender, FormClosingEventArgs e) {
this.Hide();
this.Parent = null;
e.Cancel=true;
}
To show the form after closing it this way, show it with the Show() method.
However this is probably only a workaround and you could solve the problem with another design.
Maybe it would be wise, to create a new instance of your form, every time you need it, instead of trying to reopen it every time. This also has the advantage that the form only requesires resources if it is really needed.
What you can do is add a following check before calling .Show method:
if(_Max == null || _Max.IsDisposed)
_Max = new MaxForm();
_Max.Show();
and similarly for _Min form
Whenever a form is closed, all its resources are freed. This means that you can't access the object any more, since it no longer exists - it's been freed and deleted from memory. To prevent that, you can cancel the closing of the form, and hide it instead (which will appear transparent to the user).
this.Hide();
e.Cancel=true;
An updated version of your code is as follows:
private void Max_FormClosing(object sender, FormClosingEventArgs e)
{
e.Cancel = true;
this.Hide();
this.Parent = null;
}
The solution is simple that instantiate the object of the called form in the button click event e.g.
private void buttonSetting_Click( object sender, EventArgs e )
{
***_setting = new SettingWindow();*** //When I need to show the settings window
_setting.Show();
}
create new instatnce if object is not available
if(frmRGB==nullptr || frmRGB.IsDisposed==true )
{
frmRGB= new Form();
}
Create Object inside button click event
like this
private void btn_supplier_order_Click(object sender, EventArgs e)
{
form_supplier_order so = new form_supplier_order();
so.Show();
}
I have a button click event handler with the following pseudo code:
private void btnSave_Click(object sender, EventArgs e)
{
if(txt.Text.length == 0)
this.Close();
else
// Do something else
// Some other code...
}
This is just some simple code, but the point is, when the text length equals zero, I want to close the form. But instead of closing the form the code executes the part // Some other code. After the click event handler is completely executed, then the form is closed.
I know, when I place return right after this.Close() the form will close, but I'd like to know WHY the form isn't direclty closed when you call this.Close(). Why is the rest of the event handler executed?
The rest of the event handler is executed because you did not leave the method. It is as simple as that.
Calling this.Close() does not immediately "delete" the form (and the current event handler). The form will be collected later on by the garbage collector if there are no more references to the form.
this.Close() is nothing than a regular method call, and unless the method throws an exception you will stay in the context of your current method.
Close only hides the form; the form is still alive and won't receive another Load event if you show it again.
To actually delete it from memory, use Dispose().
Answer is simple as you are executing your current method so this.Close() will be enqueued until either you explicitly returned or your current excuting method throws an exception.
Another possible solution is that if you open a new Form and want to close the current one: if you use newForm.ShowDialog() instead of newForm.Show() it doesn't close the currentForm with currentForm.Close() until the newForm is also closed.
Unless the Form is a modal form(opened with .ShowDialog()), Form.Close() disposes the form, as well. So, you cannot reopen it under any circumstances after that, despite of what others may have said. There is Form.Visible for this behavior(hiding/showing the form).
The point here is that .Close() does not return from the section it is called for several reasons. For example, you may call SomeForm.Close() from another form or a class or whatever.
Close() is just a method like any other. You have to explicitly return from a method that calls Close() if this is what you want.
Calling MessageBox.Show(frmMain,"a message","a title") adds the form "TextDialog" to the application's Application.OpenForms() forms collection, along-side the frmMain Main form itself. It remains after you close the Messagebox.
When this happens and you call the OK button delegate to close the main form, calling frmMain.Close() will not work, the main form will not disappear and the program will not terminate as it usually will after you exit the OK delegate. Only Application.Exit() will close all of the garbage messagebox "TextDialog"s.
private void btnCloseForm_Click(object sender, EventArgs e)
{
FirstFrm.ActiveForm.Close();
}
and if you want close first form and open secound form do this :
private void btnCloseForm_Click(object sender, EventArgs e)
{
FirstFrm.ActiveForm.Close();
}
private void FirstFrm_FormClosed(object sender, FormClosedEventArgs e)
{
SecounfFrm frm = new SecounfFrm ();
frm.ShowDialog();
}
or you can do somting like that :
private void btnCloseForm_Click(object sender, EventArgs e)
{
this.Hide();
}
private void FirstFrm_VisibleChanged(object sender, EventArgs e)
{
if(this.Visible == false)
{
this.Close();
}
}
private void FirstFrm_FormClosed(object sender, FormClosedEventArgs e)
{
SecounfFrm frm = new SecounfFrm ();
frm.ShowDialog();
}