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Thread safty solution?

P: n/a
If I have the problem that I can't access form controls because
it's not the main thread, can I instead store the values in global
variables, and then in the main thread have a timer that updates
the controls from the global variables?
Nov 21 '05 #1
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3 Replies


P: n/a
Dinny,

I advice you to try this walkthrough, it is in my opinion because names they
use for the fields and methods almost unreadable, however it is when you are
used to that very good.

http://msdn.microsoft.com/library/de...dcomponent.asp

I hope this helps?

Cor

"dinny" <nospam>
If I have the problem that I can't access form controls because
it's not the main thread, can I instead store the values in global
variables, and then in the main thread have a timer that updates
the controls from the global variables?

Nov 21 '05 #2

P: n/a
> I advice you to try this walkthrough, it is in my opinion because names
they
use for the fields and methods almost unreadable, however it is when you are used to that very good.


Am I to assume from your reply that using a timer to update a form is not
good ?

Nov 21 '05 #3

P: n/a
In article <Ov**************@TK2MSFTNGP09.phx.gbl>, dinny wrote:
If I have the problem that I can't access form controls because
it's not the main thread, can I instead store the values in global
variables, and then in the main thread have a timer that updates
the controls from the global variables?


I would not resort to global variables here... I would create a
delegate method that you could call using the forms Invoke method to
populate a class with the values...

Option Explicit On
Option Strict On

Imports System
Imports System.Threading
Imports System.Windows.Forms

Public Class Form1
Inherits System.Windows.Forms.Form

#Region " Windows Form Designer generated code "

Public Sub New()
MyBase.New()

'This call is required by the Windows Form Designer.
InitializeComponent()

'Add any initialization after the InitializeComponent() call

End Sub

'Form overrides dispose to clean up the component list.
Protected Overloads Overrides Sub Dispose(ByVal disposing As
Boolean)
If disposing Then
If Not (components Is Nothing) Then
components.Dispose()
End If
End If
MyBase.Dispose(disposing)
End Sub

'Required by the Windows Form Designer
Private components As System.ComponentModel.IContainer

'NOTE: The following procedure is required by the Windows Form
Designer
'It can be modified using the Windows Form Designer.
'Do not modify it using the code editor.
Friend WithEvents Button1 As System.Windows.Forms.Button
<System.Diagnostics.DebuggerStepThrough()> Private Sub
InitializeComponent()
Me.Button1 = New System.Windows.Forms.Button
Me.SuspendLayout()
'
'Button1
'
Me.Button1.Location = New System.Drawing.Point(100, 20)
Me.Button1.Name = "Button1"
Me.Button1.TabIndex = 0
Me.Button1.Text = "Button1"
'
'Form1
'
Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
Me.ClientSize = New System.Drawing.Size(292, 266)
Me.Controls.Add(Me.Button1)
Me.Name = "Form1"
Me.Text = "Form1"
Me.ResumeLayout(False)

End Sub

#End Region

Class Args
Private someText As String

Public Property Text() As String
Get
Return someText
End Get
Set(ByVal Value As String)
someText = Value
End Set
End Property
End Class

Delegate Sub GetFormValues(ByVal a As Args)

Private Sub GetValues(ByVal a As Args)
a.Text = Me.Text
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles Button1.Click
Dim th As New Thread(AddressOf ThreadProc)
th.Start()
End Sub

Private Sub ThreadProc()
Dim d As New GetFormValues(AddressOf GetValues)
Dim a As New Args

Me.Invoke(d, New Object() {a})
MessageBox.Show(a.Text)
End Sub
End Class

Obviously, you would add as many values to the args class as you needed
to access. This way, using Invoke you marshal the call back to the
forms thread, and it is perfectly safe to access the form values.
--
Tom Shelton [MVP]
Nov 21 '05 #4

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