How Do I Add Control To Container From Separate Thread

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Hi, i want to add some controls to flowlayoutpanel from async thread, but di get an error that say "Cross-thread operation not valid: Control 'ect' accessed from a thread other than the thread it was created on.".
Please help me

Antonio from italy

Posted 21-Jan-14 7:04am

prometeo2000

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2 solutions

Solution 1

ERROR : Cross-thread operation not valid: Control 'listView1' accessed from a thread other than the thread it was created on.[^]

http://stackoverflow.com/questions/5037470/cross-thread-operation-not-valid[^]

Read This[^]

Posted 21-Jan-14 7:07am

Krunal Rohit

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Ron Beyer · Accepted Answer · 2014-01-21T07:08:00

Solution 2

Its relatively simple, you have to invoke the adding/removing/modifying of a control on the UI thread:

C#

flowLayoutPanel1.Invoke((MethodInvoker) delegate {
    //Code to add your control to the panel here.
});

You can construct the control outside of the invoke, and only put the add inside the invoke delegate. This is just one way of doing it, there are other ways. For example, before calling flowLayoutPanel1.Invoke you should check first if a cross-thread operation will really occur by checking the value of flowLayoutPanel1.InvokeRequired. If that is true, then do the above, if not, just add it directly to the panel.

Posted 21-Jan-14 7:08am

Ron Beyer

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prometeo2000 21-Jan-14 15:29pm

Hi Ron,
Thank you for your suggest, i have try it and ... work fine!!!
Here my code...

Ti ringrazio anche in Ialiano... nel caso avessi commesso qualche errore in inglese, visto che non è una lingua che conosco benissimo. Ciao

Imports System.Threading

Public Class Form1

Dim t As Thread
Delegate Sub AddControlsCallBack([btn] As Button)

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

StopThread()
FlowLayoutPanel1.Controls.Clear()

t = New Thread(AddressOf AddControls)
t.Start()

End Sub

Private Sub AddControls()

For i As Integer = 0 To 100

Dim b As New Button
b.Text = "Button" & i

Thread.Sleep(1000) 'some hard work

If FlowLayoutPanel1.InvokeRequired Then
Dim ctrlCallBack As New AddControlsCallBack(AddressOf addButtons)
Me.Invoke(ctrlCallBack, New Object() {b})
Else
FlowLayoutPanel1.Controls.Add(b)
End If

Next

End Sub

Private Sub addButtons(ByVal b As Button)

FlowLayoutPanel1.Controls.Add(b)

End Sub

Private Sub StopThread()

If Not t Is Nothing Then
If t.IsAlive Then t.Abort()
End If

End Sub

Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click

StopThread()

End Sub

End Class