I'd need a way to cause the program to crash on purpose when i click a button. But nothing comes to my mind that would still allow me to compile the program. any code that causes a hard crash for whatever reason. in particular i need it to close and not be able to continue. My beta testers need to test the recovery after crash feature. Thanks!
these things never happen when they should..
How about just throwing an unhandled exception?
Private Sub btnCrash_Click(sender As System.Object, e As System.EventArgs) Handles btnCrash.Click
Throw New System.Exception("The program has crashed catastrophically!")
End Sub
To effectively kill the process use Environment.FailFast() in a button click handler, like this:
Protected Sub buttonCrash_Click(sender As Object, e As EventArgs) Handles buttonCrash.Click
Environment.FailFast()
End Sub
This will not generate any exceptions, etc., it is the same as going to Windows Task Manager and killing the process.
Here is the documentation for Environment.FailFast Method (String)
How about the Environment.FailFast method?
Private Sub btn_click(...)
Environment.FailFast("Failure!")
End Sub
Related
I made a projet a month ago in C# where I used application settings to save data. This time, I'm making a project in VB .NET where I need to store data. I have a textbox where the user input a certain key and if he gets it right, it sets a setting to true. Here's the code.
Public Class Form4
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
If TextBox1.Text = ("CF4A438C1F68D" Or "7552B2C629D11" Or "9C9C94A73141A" Or "7EE3998DAB3D3" Or "FC4DABC9CA7EA" Or "FDEE4B1F2C113" Or "D773E97B47531" Or "AABBBF181D39A" Or "36F37B39D19A5") Then
Properties.Settings.Default.ActivatedVersion = True
Properties.Settings.Default.Save()
End If
End Sub
End Class
Unfortunately, when I write Properties, it doesn't work. How can I do this?
In VB, you use My.Settings rather than Properties.Settings.Default.
Also, you don't necessarily need to call Save explicitly as it will happen automatically, by default, when the application exits. It won't happen if the application crashes but, if you have done the right thing and handled the UnhandledException event, the application will not crash, even if an unhandled exception is thrown.
I'm currently working with the iTunes COM with .NET, and something I came across previously, which stopped me using it, has happened again and I can't for the life of me figure it out.
When I go to close iTunes during or after my program has closed, it tells me something is still using the "Application Scripting Interface", COM is still connected.
This is what I have (removed what is not required)
Private Sub frmMain_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
AddHandler itunes.OnAboutToPromptUserToQuitEvent, AddressOf itunes_OnAboutToPromptUserToQuitEvent
End Sub
Private Sub itunes_OnAboutToPromptUserToQuitEvent()
System.Runtime.InteropServices.Marshal.ReleaseComObject(itunes)
End Sub
So, the above code does disconnect the COM to the extent that I need to restart iTunes to use it again, but, it doesn't get rid of the Application Scripting error. Meaning, I still need to click quit after the error dialog comes up. Everything else works fine, apart from this.
Any idea?
-- I've had a look at other questions that had this issue, but none of them resolved it for me. I'm not sure if the event doesn't work anymore with this current version of iTunes, but, it doesn't seem to work currently either way.
Had same issue with COM and Office, this solved it;
While System.Runtime.InteropServices.Marshal.ReleaseComObject(itunes) <> 0
Application.DoEvents()
End While
I'm writing an examination piece of software for my workplace and would like to know how I can trap and cancel key-presses such as:
ALT+F4
WIN+TAB
ALT+TAB
WIN
CTRL+ALT+DEL
I'm aware CTRL+ALT+DEL may not be possible, but if any of this is it'll be a step in the right direction!
Ideally I want to prevent the action, and then open a new form I've created saying 'Unauthorised keypress'
as #SQLHound link relates... us the FormClosing event to handle what happens when a user attempts to close. But if you want to block a boot attempt, then #Plutonix suggestion may help. Something along these lines...
Private Sub Form1_FormClosing(sender As Object, e As FormClosingEventArgs) Handles Me.FormClosing
Dim splashScreen as New Form
splashScreen.OpenDialog
e.Cancel=True
End Sub
I'm looking into disposing of resources and getting a little mixed up over the different ways to do it.
I've just found out that using Close() on a form shown with ShowDialog() only actually hides it and doesn't completely kill it off, so to speak. While this is useful for what I want at the moment, I'm now worrying about memory leaks elsewhere.
After using ShowDialog(), should I always call Dispose() on the form or use a Using block? Is there a difference? Or will the form be automatically disposed of when exiting the subroutine is was created in? For example, one of my typical simple usages:
Private Sub btnEdit_Click(sender As System.Object, e As System.EventArgs) Handles btnEdit.Click
Dim frm As New frmSomething()
frm.ShowDialog()
'frm is exited by clicking the X or using Close()
'At this point, frm is still in memory. Is it automatically disposed of
'after the End Sub here, or should I do frm.Dispose() ?
End Sub
It won't be automatically disposed, no. It may well not cause a problem, and there may well be a finalizer to do everything that's required, so the cost would just be some extra resources before the finalizer runs (and a longer delay before eventual GC) but it would be better to dispose it explicitly - ideally with a Using statement:
Using frm As New frmSomething()
frm.ShowDialog()
End Using
I'm working with VB.net.
I’m having problems while I connect my application to my database today so I wanted to add an error handling to close the form.
The problem is that when I put Me.close in a form, this form still open. I used the Form.Closing event handler to verify that it was called, and then ran my application in step by step which showed that the event handler was called, but the application continues and the errors appears to the user.
Does anyone knows how to close a form properly without closing the application?
Close will close a form, but only if it has no more code to run.
That is, there are two conditions that need to be fulfilled for a form to close:
Close must be called
Any method still running must be left
I suspect that another method is still running code, for instance a loop or other code that causes the form to remain open.
Furthermore, the form will get re-opened automatically once you start accessing its members form elsewhere, due to an infuriating property of VB to auto-instantiate forms.
You can check for what reason the form don't get closed.
Private Sub Form1_Closing(ByVal sender As System.Object, _
ByVal e As System.Windows.Forms.FormClosingEventArgs) _
Handles MyBase.FormClosing
MsgBox(e.CloseReason.ToString)
End Sub
You can add to the Form_Closing event the following
The e.Cancel will close the open operation. But first check the reason.
Private Sub Form1_Closing(ByVal sender As System.Object, _
ByVal e As System.Windows.Forms.FormClosingEventArgs) _
Handles MyBase.FormClosing
e.Cancel = True
End Sub
Technically the form is closed but not disposed, which means you can still reach the object but all controls in it are no longer reachable.
So you will have to call dispose from somewhere to get rid of it completely.