Still celebrating National IT Professionals Day with 3 months of free Premium Membership. Use Code ITDAY17

x
?
Solved

Cross-thread operation not valid: Control

Posted on 2010-11-26
2
Medium Priority
?
539 Views
Last Modified: 2012-05-10

I am trying to load a combo box from a web service.  I am doing this through a callback Display lists.  Display lists receives the Lists parameter fine when called. So the web service call itself is working fine.   But when i tries to bind the list to the combo box i get the error  "Cross-thread operation not valid: Control '' accessed from a thread other than the thread it was created on."  

I have tried re-factoring this in many ways using background workers etc I even tried to create my own custom control who sole purpose was to load this data.  All methods seem to give me the same error.




 
Private WithEvents M_List As New IContact.List

  
Private Sub ctrl_ImportGroups_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Me.M_List.LoadLists()
End Sub



Public Sub DisplayLists(ByVal Lists As List(Of IContact.List)) Handles M_List.onLoadListsCompleted
        Me.cmbIContactList.DataSource = Lists
        Me.cmbIContactList.ValueMember = "listid"
        Me.cmbIContactList.DisplayMember = "name"
End Sub

Open in new window

0
Comment
Question by:Kevin Robinson
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
2 Comments
 
LVL 13

Accepted Solution

by:
Naman Goel earned 2000 total points
ID: 34218607
The Reason:
If you are from the old COM/COM+ Days, you must remember that an STA (Single Threaded Apartment) can only be accessed by the thread that originally created it. All the controls on the form are created by the main thread of the application, so only the main thread can update it. When your asynch webservice call returns it is calling the DisplayLists(ByVal Lists As List(Of IContact.List)) Handles M_List.onLoadListsCompleted
event handler in the context of a different thread. This thread is not allowed to touch any controls on the form

Please refer to modified code
Private WithEvents M_List As New IContact.List

  
Private Sub ctrl_ImportGroups_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Me.M_List.LoadLists()
End Sub

Private Delegate Sub UpdateUI(ByVal Lists As List(Of IContact.List))


Public Sub DisplayLists(ByVal Lists As List(Of IContact.List)) Handles M_List.onLoadListsCompleted
        Me.Invoke(New UpdateUI(AddressOf UpdateUIMethod), Lists)
End Sub

Public Sub UpdateUIMethod(ByVal Lists As List(Of IContact.List))
	Me.cmbIContactList.DataSource = Lists
        Me.cmbIContactList.ValueMember = "listid"
        Me.cmbIContactList.DisplayMember = "name"
End Sub

Open in new window

0
 
LVL 3

Author Closing Comment

by:Kevin Robinson
ID: 34225141
Great.  Almost had that actully
0

Featured Post

Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Here I am going to explain creating proxies at runtime for WCF Service. So basically we use to generate proxies using Add Service Reference and then giving the Url of the WCF service then generate proxy files at client side. Ok, what if something ge…
This article shows how to deploy dynamic backgrounds to computers depending on the aspect ratio of display
In this video, Percona Director of Solution Engineering Jon Tobin discusses the function and features of Percona Server for MongoDB. How Percona can help Percona can help you determine if Percona Server for MongoDB is the right solution for …
In response to a need for security and privacy, and to continue fostering an environment members can turn to for support, solutions, and education, Experts Exchange has created anonymous question capabilities. This new feature is available to our Pr…

715 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question