invalid exception {"Invoke or BeginInvoke cannot be called on a control until the wi

[MffM]

Hi all

i have a project in vb.net some times at run time this message appear

InvalidOperationException was unhandled

{"Invoke or BeginInvoke cannot be called on a control until the window handle has been created."}


i don't know why and i didn't find any logic when it's appear because when i run my project some time its appear and some times it doesn't appear.

i read alot of articals all of them talk about thread and UI
but i didn't use thread in my project , i used alot of select statments, insert and update to the data base , for loops , show forms and show dialogs .

please how can i fix this problems and how can i know where is the problem.

this is the details of the exception

System.InvalidOperationException was unhandled
Message="Invoke or BeginInvoke cannot be called on a control until the window handle has been created."
Source="System.Windows.Forms"
StackTrace:
at System.Windows.Forms.Control.MarshaledInvoke(Contr ol caller, Delegate method, Object[] args, Boolean synchronous)
at System.Windows.Forms.Control.BeginInvoke(Delegate method, Object[] args)
at System.Windows.Forms.Label.OnFrameChanged(Object o, EventArgs e)
at System.Drawing.ImageAnimator.ImageInfo.OnFrameChan ged(EventArgs e)
at System.Drawing.ImageAnimator.ImageInfo.set_Frame(I nt32 value)
at System.Drawing.ImageAnimator.AnimateImages50ms()
at System.Threading.ThreadHelper.ThreadStart_Context( Object state)
at System.Threading.ExecutionContext.Run(ExecutionCon text executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()

note in some articals i read about calling the method begininvoke(delegate) so i did this and called the begininvoke method in the load procuder of my form and this what i have written

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

Dim method As System.Delegate

Dim returnValue As IAsyncResult

returnValue = Me.BeginInvoke(method)


End Sub

i know there is something missing what is it i need a code exampe please


thanks in advance:)

[.ben]

Your form is still loading so what you've written in your load event handler is invalid until the form has finished loading.

Why do you have that code in there?

[MffM]

Tahnks for replying my message

that code i added to avoid the exception error message but it's not usefull and it's wrong.

now what i have to do to avoid the exeception message?
u said "Your form is still loading so what you've written in your load event handler is invalid until the form has finished loading.
"
how can i know when my form finish the loading to start my procuders?
note: usually this error appear when i close the form some time it's not

please advice

Thanks

[.ben]

I took a closer look at your stack trace, and saw a class which I haven't used before: the imageanimator.

I played with it and it does run on another thread and I think in the eventhandler you've written, you are calling members of a UI control (a label I guess).

Since you are calling it from another thread you will get that exception. So you need to make that code thread safe.

Your current eventhandler could look like this:

Private Sub OnFrameChanged(ByVal o As Object, ByVal e As EventArgs)
'stuff I'd like to do

x += 1
Label1.Text = "hihi" & x
End Sub


this is not thread safe!

to make it work you have to do it like this:

Private Sub OnFrameChanged(ByVal o As Object, ByVal e As EventArgs)
'stuff I'd like to do

x += 1
ChangeTheLabel()
End Sub

Private Delegate Sub MyDelegate()

Private Sub ChangeTheLabel()
If Label1.InvokeRequired Then
Label1.BeginInvoke(New MyDelegate(AddressOf ChangeTheLabel))
Return
End If
Label1.Text = "hihi" & x
End Sub

Still I could be way off, if you could show some code I wouldn't have to do so much guesswork :)

[MffM]

Hi

in my project i have many labels it contain animaited image
mainly all label have 3 methods
this is one of my label's method
Me.lblclose.Image = "lblclose.Image" ''' this image is animated
Private Sub lblclose_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles lblclose.Click
' when click on the close button we should confirm that all guops are set visable false the the main menu set visable true
gMainmenu.Visible = True
btnpell.Visible = True
btnCansel.Visible = True

gMainDishes.Visible = False
gRice.Visible = False
gPell.Visible = False
gapp.Visible = False
gdrink.Visible = False
gSweet.Visible = False
lblclose.Visible = False


End Sub


Private Sub lblclose_MouseHover(ByVal sender As Object, ByVal e As System.EventArgs) Handles lblclose.MouseHover
lblclose.BorderStyle = BorderStyle.Fixed3D
End Sub

Private Sub lblclose_MouseLeave(ByVal sender As Object, ByVal e As System.EventArgs) Handles lblclose.MouseLeave
lblclose.BorderStyle = BorderStyle.None
End Sub

where i have to put the safe thread in my code and i have to do it to each label

thanks in advance

[MffM]

i remove all event mouseover and mouse leave in the laels and the error sitll occured

i note something the error happen when i close the form
it enter the deispose method put it didn't finish it

this haapen some times not always

[.ben]

I'm unable to duplicate that behaviour, even with labels containing animated gifs.

Put the threadsafe code in all code being called by the OnFrameChanged eventhandler and see if that helps.