multi-threading

  • Thread starter Thread starter Ian Williamson
  • Start date Start date
I

Ian Williamson

I wanted to keep this one alive as it seems to have
gotten lost over the weekend...

....

Thanks again for responding Chris.

I have worked through many samples which show updating
various objects using a thread outside the UI. What they
all fail to do however is show how to process "something"
within the UI thread while the background thread is
running.

Whenever I try to perform something in the UI after I
have started my background thread, it completely takes
over and the background thread fails to get it's time-
slice.

I am including some sample code to highlight my problem.
I am sure my newbness is causing me to overlook something
obvious.

----

using System;
using System.Drawing;
using System.Collections;
using System.Windows.Forms;
using System.Data;
using System.Threading;
using System.ComponentModel;

namespace WindowsApplication1
{
public class Form1 : System.Windows.Forms.Form
{
private System.Windows.Forms.Label
TextLabel;

private EventHandler autoSaveDelegate;
private System.Windows.Forms.Button
button1;
private System.Windows.Forms.Button
button2;
private System.Windows.Forms.Label label1;
bool autoSaveComplete = false;

protected override void Dispose( bool
disposing )
{
base.Dispose( disposing );
}

static void Main()
{
Application.Run(new Form1());
}

public Form1()
{
InitializeComponent();
autoSaveDelegate = new
EventHandler(UpdateTextLabel);
}

private void button1_Click(object sender,
System.EventArgs e)
{
this.TextLabel.Text = "Updating";
new Thread(new ThreadStart
(StatusFeedback)).Start();
this.autoSaveComplete = true;
// the call to this method will
cause the new thread to wait until this UI method has
completed
this.PrintNumbers();
}

private void PrintNumbers()
{
for (int i = 0; i < 1000; i++)
{
label1.Text = i.ToString
();
label1.Refresh();
Thread.Sleep(5);
}
}

private void button2_Click(object sender,
System.EventArgs e)
{
this.autoSaveComplete = false;
}

private void StatusFeedback()
{
while (this.autoSaveComplete)
{
this.Invoke
(autoSaveDelegate);
Thread.Sleep(250);
}
}

private void UpdateTextLabel(object
sender,EventArgs e)
{
this.TextLabel.Text =
TextLabel.Text + ".";
this.TextLabel.Refresh();
}

private void InitializeComponent()
{
this.TextLabel = new
System.Windows.Forms.Label();
this.button1 = new
System.Windows.Forms.Button();
this.button2 = new
System.Windows.Forms.Button();
this.label1 = new
System.Windows.Forms.Label();
this.SuspendLayout();
//
// TextLabel
//
this.TextLabel.BackColor =
System.Drawing.SystemColors.ActiveCaptionText;
this.TextLabel.Location = new
System.Drawing.Point(48, 64);
this.TextLabel.Name = "TextLabel";
this.TextLabel.Size = new
System.Drawing.Size(176, 16);
this.TextLabel.TabIndex = 0;
//
// button1
//
this.button1.Location = new
System.Drawing.Point(48, 104);
this.button1.Name = "button1";
this.button1.TabIndex = 1;
this.button1.Text = "Start";
this.button1.Click += new
System.EventHandler(this.button1_Click);
//
// button2
//
this.button2.Location = new
System.Drawing.Point(152, 104);
this.button2.Name = "button2";
this.button2.TabIndex = 2;
this.button2.Text = "Stop";
this.button2.Click += new
System.EventHandler(this.button2_Click);
//
// label1
//
this.label1.Location = new
System.Drawing.Point(112, 24);
this.label1.Name = "label1";
this.label1.Size = new
System.Drawing.Size(40, 23);
this.label1.TabIndex = 3;
this.label1.Text = "label1";
//
// Form1
//
this.AutoScaleBaseSize = new
System.Drawing.Size(5, 13);
this.ClientSize = new
System.Drawing.Size(292, 266);
this.Controls.Add(this.label1);
this.Controls.Add(this.button2);
this.Controls.Add(this.button1);
this.Controls.Add(this.TextLabel);
this.Name = "Form1";
this.ResumeLayout(false);

}
}
}


Cheers, Ian



-----Original Message-----
Basically any control at all must only be affected from the primary thread
(the one created with Main and continued in
Click to expand...
Application.Run). If any other
 
Hi Ian,

I'm no expert. However, your Thread.Sleep(250) call will pause the
background thread by 250 mS (that is the context where it executes). Is
this what you want?

I think your code is correct, from a design standpoint. At least, this is
the basic pattern that I have used.

Dick

--
Richard Grier (Microsoft Visual Basic MVP)

See www.hardandsoftware.net for contact information.

Author of Visual Basic Programmer's Guide to Serial Communications, 3rd
Edition ISBN 1-890422-27-4 (391 pages) published February 2002.
 
Good article there Fernando. Was as simple as including
Application.DoEvents().

Thanks.
 
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