VB Cross-Thread Operation not valid

[alecsillidan]

Hello again!
I encountered another strange thing while programming for fun, this is the sub where I get an error:

Code: [Select]

    Private Sub checkversion()
        Me.VersionTableAdapter.Fill(Me.Update.version)
        onlineversion1 = ListBox1.SelectedItem("version").ToString()
        onlineversion = CDbl(onlineversion1)
        AccessControl()
        textonline.Text = "Versiune Online: " & onlineversion
        Label1.Text = onlineversion1
        If version = onlineversion Then

        Else
            actualizaredisp = 1
            MsgBox("A aparut o versiune mai noua! Apasati Ok pentru a face update." & vbLf & "Versiunea programului: " & version & vbLf & "Versiunea noua: " & onlineversion & vbLf & vbLf & "Apasati F1 pentru actualizare!", MsgBoxStyle.YesNo, "Actualizare disponibila!")
        End If
    End Sub
I get the error "Cross-thread operation not valid: Control 'Form1' accessed from a thread other than the thread it was created on."

Code: [Select]

System.InvalidOperationException was unhandled by user code
  Message=Cross-thread operation not valid: Control 'pornire' accessed from a thread other than the thread it was created on.
  Source=System.Windows.Forms
  StackTrace:
       at System.Windows.Forms.Control.get_Handle()
       at System.Windows.Forms.Control.get_InternalHandle()
       at System.Windows.Forms.Control.get_CreateParams()
       at System.Windows.Forms.Label.get_CreateParams()
       at System.Windows.Forms.Control.SizeFromClientSize(Int32 width, Int32 height)
       at System.Windows.Forms.Control.SizeFromClientSize(Size clientSize)
       at System.Windows.Forms.Label.GetBordersAndPadding()
       at System.Windows.Forms.Label.GetPreferredSizeCore(Size proposedConstraints)
       at System.Windows.Forms.Control.GetPreferredSize(Size proposedSize)
       at System.Windows.Forms.Label.GetPreferredSize(Size proposedSize)
       at System.Windows.Forms.Control.get_PreferredSize()
       at System.Windows.Forms.Label.AdjustSize()
       at System.Windows.Forms.Label.OnTextChanged(EventArgs e)
       at System.Windows.Forms.Control.set_Text(String value)
       at System.Windows.Forms.Label.set_Text(String value)
       at centrala_concurs.pornire.Button10_Click() in C:\Users\alecs_000\Documents\Visual Studio 2010\Projects\centrala_concurs\centrala_concurs\pornire.vb:line 106
       at centrala_concurs.pornire.BackgroundWorker1_DoWork(Object sender, DoWorkEventArgs e) in C:\Users\alecs_000\Documents\Visual Studio 2010\Projects\centrala_concurs\centrala_concurs\pornire.vb:line 116
       at System.ComponentModel.BackgroundWorker.OnDoWork(DoWorkEventArgs e)
       at System.ComponentModel.BackgroundWorker.WorkerThreadStart(Object argument)
  InnerException:

I searched on Google but didn't actually understand the code and I don't use pieces of code that I don't understand.

Thank you again:D

[BC_Programmer]

When accessing Windows Forms from another thread, you need to use Invoke on the target control. eg. to set the text of a label from another thread:

Code: [Select]

Label1.Text="hello"


will throw an error.

Code: [Select]

Me.Invoke((Function() Label1.Text="hello"))
I'm not 100% Sure for VB; this is afaik the equivalent to this C#:

Code: [Select]

this.Invoke((MethodInvoker)(()=>Label1.Text="hello"));


[alecsillidan]

Figured it out, works now:D
now i'm getting another error:

Code: [Select]

        If version = onlineversion Then

        Else
            MsgBox("A aparut o versiune mai noua! Apasati Ok pentru a face update." & vbLf & "Versiunea programului: " & version & vbLf & "Versiunea noua: " & onlineversion & vbLf & vbLf & "Apasati F1 pentru actualizare!", MsgBoxStyle.YesNo, "Actualizare disponibila!")
            actualizare.Show()
        End If
An error occurred creating the form. See Exception.InnerException for details.  The error is: Conversion from string "" to type 'Double' is not valid.

Visual Studio shows that the error is at actualizare.show()

[BC_Programmer]

It works setting the label text, the error occures in line "If version = onlineversion Then" and I'm not getting the ideea...how i'm supposed to make the if condition if vb can't read those variables or idk why i'm getting that error:|

The exception message indicates the error is caused by attempting to set the text of the label:

StackTrace:
       at System.Windows.Forms.Control.get_Handle()
       at System.Windows.Forms.Control.get_Intern alHandle()
       at System.Windows.Forms.Control.get_Create Params()
       at System.Windows.Forms.Label.get_CreatePa rams()
       at System.Windows.Forms.Control.SizeFromCl ientSize(Int32 width, Int32 height)
       at System.Windows.Forms.Control.SizeFromCl ientSize(Size clientSize)
       at System.Windows.Forms.Label.GetBordersAn dPadding()
       at System.Windows.Forms.Label.GetPreferred SizeCore(Size proposedConstraints)
       at System.Windows.Forms.Control.GetPreferr edSize(Size proposedSize)
       at System.Windows.Forms.Label.GetPreferred Size(Size proposedSize)
       at System.Windows.Forms.Control.get_Prefer redSize()
       at System.Windows.Forms.Label.AdjustSize()
       at System.Windows.Forms.Label.OnTextChange d(EventArgs e)
       at System.Windows.Forms.Control.set_Text(String value)
       at System.Windows.Forms.Label.set_Text(String value)
       at centrala_concurs.pornire.Button10_Click() in C:\Users\alecs_000\Documents\Visual Studio 2010\Projects\centrala_concurs\centrala_concurs\pornire.vb:line 106
       at centrala_concurs.pornire.BackgroundWork er1_DoWork(Object sender, DoWorkEventArgs e) in C:\Users\alecs_000\Documents\Visual Studio 2010\Projects\centrala_concurs\centrala_concurs\pornire.vb:line 116
       at System.ComponentModel.BackgroundWorker. OnDoWork(DoWorkEventArgs e)
       at System.ComponentModel.BackgroundWorker. WorkerThreadStart(Object argument)

What is line 106 and 116 of "pornire.vb"?

[alecsillidan]

nvm i'm noob, i modified the previous post, read it again please:))

[BC_Programmer]

See Exception.InnerException for details.

Sounds like an error within the Form_Load to me, but without the InnerException it's hard to say exactly where it is.

EDIT: if you are using Visual Studio, the "Exception Helper" should let you look at the inner exception.

[alecsillidan]

It's working! I was using a double variable with a string text =))
Thank you dude, you're life saver