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Posted 7 Oct 2006

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.


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


1- Create your thread:

Private Strt As System.Threading.Thread

2- Start your thread wherever you want:

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

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


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)) 
    ' 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:

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:
Have a nice day :)


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


About the Author

Software Developer (Senior) InfraDrive
Egypt Egypt
Egyptian freelance programmer and the founder of InfraDrive, Inc.


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Comments and Discussions

Generalcross thread operation Pin
evergreen50115-May-07 5:07
memberevergreen50115-May-07 5:07 
Generalthis is easy yet brilliant Pin
sunlight2-May-07 18:46
membersunlight2-May-07 18:46 
QuestionPlease excuse my ignorance... Pin
HD-P26-Apr-07 11:38
memberHD-P26-Apr-07 11:38 
GeneralAny Solution for Same In .net 3.0 Pin
sumit_4palz25-Apr-07 0:04
membersumit_4palz25-Apr-07 0:04 
GeneralRe: Any Solution for Same In .net 3.0 Pin
elagizy25-Apr-07 4:00
memberelagizy25-Apr-07 4:00 
AnswerRe: Any Solution for Same In .net 3.0 Pin
MaxtorM1236-Nov-08 6:50
memberMaxtorM1236-Nov-08 6:50 
QuestionHOW TO SOLVE: "Cross thread operation not valid" (DIRTY WAY) Pin
Miroslav Stampar12-Apr-07 5:16
memberMiroslav Stampar12-Apr-07 5:16 
GeneralClear, concise and works perfectly! Pin
VorTechS11-Apr-07 22:21
memberVorTechS11-Apr-07 22:21 
I've been looking for a while for a simple explanation of how thread-safe GUI operations can be performed.

This did the trick, and instantly resolved a major headache in my new app!

Thank you!
GeneralThx Pin
todwag4-Apr-07 5:27
membertodwag4-Apr-07 5:27 
GeneralWelcome all Pin
elagizy17-Mar-07 22:08
memberelagizy17-Mar-07 22:08 
GeneralThanks a lot! Pin
Raymond S.K.17-Mar-07 19:27
memberRaymond S.K.17-Mar-07 19:27 
GeneralThanks Pin
LOKIN SHAH5-Mar-07 16:35
memberLOKIN SHAH5-Mar-07 16:35 
GeneralThanks! Pin
Member #229774215-Feb-07 9:52
memberMember #229774215-Feb-07 9:52 
GeneralThanks!!! Pin
Member #25547358-Feb-07 16:52
memberMember #25547358-Feb-07 16:52 
GeneralThx - this solution rocks Pin
Andy3231-Jan-07 12:55
memberAndy3231-Jan-07 12:55 
GeneralVery nice Pin
todd200011-Jan-07 7:01
membertodd200011-Jan-07 7:01 
GeneralWorks in C# too [modified] Pin
iamstarbuck10-Dec-06 23:22
memberiamstarbuck10-Dec-06 23:22 
GeneralOMG, thank you so much Pin
Vinc__426-Oct-06 6:51
memberVinc__426-Oct-06 6:51 
GeneralThnaks Pin
UnRusoDeCaracas25-Oct-06 10:36
memberUnRusoDeCaracas25-Oct-06 10:36 
GeneralHi Pin
Marco225020-Oct-06 13:45
memberMarco225020-Oct-06 13:45 
GeneralRe: Hi Pin
elagizy20-Oct-06 22:05
memberelagizy20-Oct-06 22:05 
GeneralGreat! Pin
snakes3x11-Oct-06 21:04
membersnakes3x11-Oct-06 21:04 
GeneralRe: Great! Pin
elagizy12-Oct-06 12:03
memberelagizy12-Oct-06 12:03 

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