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How to solve "Cross thread operation not valid"

, 7 Oct 2006
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how to access a control from another thread which didn't create this control.
how to access a control from another thread which didn't create this control.

I faced this issue more than 1 time, I decided to collect info about it and made some changes on the code to simplify this problem to you cause it's really annoying and confusing to work with threading stuff. Here is a small code solves this problem FOREVER and in ANY case.

Error:

Cross thread operation not valid: Control "XXXXXXXXXX" accessed from a thread other than the thread it was created.

Solution:

1- Create your thread:

 Private Strt As System.Threading.Thread   


2- Start your thread wherever you want:

  Strt = New System.Threading.Thread(AddressOf MyThread1)
  Strt.Start()


3- Add the thread sub (MyThread1) and put whatever you want and remember that the lines which access a control from this thread will be separated to into another sub (the Delegate sub)

 Sub MyThread1
       ' Working code
       ' Working code
       ' Working code
       ' Working code
       ' Working code
       ' Working code

       AccessControl()

End Sub


From the previous code you will notice 2 things:
1st: AccessControl the sub which will be delegated.
2nd: ' Working code - which doesn't need a delegate to get it work. In other mean, it doesn't show up the error message you receive.

4- and finally, add the delegated sub:

Private Sub AccessControl()
        If Me.InvokeRequired Then
            Me.Invoke(New MethodInvoker(AddressOf AccessControl)) 
        Else
    ' Code wasn't working in the threading sub
    ' Code wasn't working in the threading sub
    ' Code wasn't working in the threading sub
    ' Code wasn't working in the threading sub
    ' Code wasn't working in the threading sub
            Button2.Visible = True
            Button3.Visible = True
            Opacity = 1
            ShowInTaskbar = True
        End If
    End Sub


From the previous code you will notice that all the codes which wasn't working in the threading sub will be added after "Else" line.
examples for some codes which needs to be delegated:
(Control).Visible
Me.Opacity
Me.ShowInTaskbar

I hope i simplified it enough, and now no worry about this issue again.
Special thanks to jmcilhinney for his help. You can also find this article at this link:
http://www.bitsnips.com/forums/viewtopic.php?p=102#102
Have a nice day Smile | :)

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

About the Author

Elagizy
Software Developer (Senior) InfraDrive
Egypt Egypt
Egyptian freelance programmer and the founder of InfraDrive, Inc.
 
Check:
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Comments and Discussions

 
QuestionNo need to use Delagates PinmemberTino Fourie25-Jan-14 23:33 
GeneralMy vote of 5 Pinmemberthams13-Jul-13 8:24 
QuestionCross thread Pinmembersabuni5-Jan-13 11:05 
GeneralMy vote of 5 PinmemberDisactive16-Dec-12 5:52 
QuestionNice Article PinmemberSatish_Tijare21-Oct-12 19:57 
GeneralMy vote of 5 [modified] PinmemberOsama El Shammari24-Jul-12 11:30 
Thank you... really simple and easy solution...
Thank you again...

modified 23-Mar-13 4:15am.

GeneralYou Rock! PinmemberTimmyTwins3-Jul-12 12:55 
GeneralRe: You Rock! PinmemberJoBrittain6-Jul-12 12:18 
QuestionMy vote Pinmemberkmf7-Dec-11 23:10 
GeneralMy vote of 5 Pinmembergafoor123-Nov-11 19:55 
QuestionAlternative Method Pinmemberjlopez78814-Oct-11 8:24 
GeneralMy vote of 5 PinmemberSunasara Imdadhusen9-Sep-11 3:19 
GeneralMy vote of 5 PinmemberNanda_MR13-Mar-11 23:34 
GeneralI laughed a lot :) PinmemberMember 102216226-Oct-10 23:17 
GeneralYou missed the point. PinmemberElagizy27-Oct-10 4:14 
GeneralMy vote of 5 PinmemberL3CodeProject22-Oct-10 10:47 
GeneralSimply Great!! Pinmemberrahu_12221-Sep-10 20:37 
Generalthanks :) :) PinmemberArunJoseph 471639512-Sep-10 5:30 
GeneralThank You Pinmemberjb.jigar30-Jul-10 8:39 
GeneralMy vote of 5 Pinmemberjb.jigar30-Jul-10 8:11 
QuestionWhat if the method is a handler of a PropertyChanged Event from an updated class variable? Pinmemberbretddog1-Apr-10 0:01 
AnswerRe: What if the method is a handler of a PropertyChanged Event from an updated class variable? PinmemberElagizy1-Apr-10 7:53 
GeneralIf it doesn't work for anyone try this... PinmemberMichaelsg22-Mar-10 23:14 
GeneralRe: If it doesn't work for anyone try this... PinmemberElagizy1-Apr-10 7:56 
GeneralWrap 'em up :) PinmemberDerek R. White13-Mar-10 15:27 

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