Component Scope Problem

[brentnewbury]

Hiya all,

I'm having problems when trying to change the value of a textbox from a thread. I've also tried creating a function inside the Form1 class then calling it from within the thread, but that doesn't seem to work either.

Here is the code:
[tt]using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.Threading;

namespace ComponentScopeTesting
{
/// <summary>
/// Summary description for Form1.
/// </summary>
public class Form1 : System.Windows.Forms.Form
{
private System.Windows.Forms.Button button1;
public System.Windows.Forms.TextBox textBox1;
/// <summary>
/// Required designer variable.
/// </summary>
private System.ComponentModel.Container components = null;

public Form1()
{
//
// Required for Windows Form Designer support
//
InitializeComponent();

//
// TODO: Add any constructor code after InitializeComponent call
//
}

/// <summary>
/// Clean up any resources being used.
/// </summary>
protected override void Dispose( bool disposing )
{
if( disposing )
{
if (components != null)
{
components.Dispose();
}
}
base.Dispose( disposing );
}

#region Windows Form Designer generated code
/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
private void InitializeComponent()
{
this.button1 = new System.Windows.Forms.Button();
this.textBox1 = new System.Windows.Forms.TextBox();
this.SuspendLayout();
//
// button1
//
this.button1.Location = new System.Drawing.Point(16, 224);
this.button1.Name = "button1";
this.button1.TabIndex = 0;
this.button1.Text = "button1";
this.button1.Click += new System.EventHandler(this.button1_Click);
//
// textBox1
//
this.textBox1.Location = new System.Drawing.Point(16, 16);
this.textBox1.Name = "textBox1";
this.textBox1.TabIndex = 1;
this.textBox1.Text = "textBox1";
//
// Form1
//
this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
this.ClientSize = new System.Drawing.Size(292, 266);
this.Controls.Add(this.textBox1);
this.Controls.Add(this.button1);
this.Name = "Form1";
this.Text = "Form1";
this.ResumeLayout(false);

}
#endregion

/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
Application.Run(new Form1());
}

private void button1_Click(object sender, System.EventArgs e)
{
TestThread oTest = new TestThread();
Thread oThread = new Thread(new ThreadStart(oTest.EntryPoint));

oThread.Start();

Thread.Sleep(10);

oThread.Abort();
}

public class TestThread : Form1
{
public void EntryPoint()
{
this.textBox1.Text = "Hello World";
MessageBox.Show("Test", "Test", MessageBoxButtons.OK, MessageBoxIcon.Information);
}
}
}
}[/tt]

Thank you for your time,

Brent Newbury

 

[brentnewbury]

Anyone?

I just want to know how to access a component like a textbox or button outside of the form scope.

Can anyone help?

Brent

 

[chiph]

Windows Forms are single-threaded. You can only safely change a value in them from the thread that created the form unless you use the BeginInvoke method along with a delegate. You may still have repaint problems even after that, depending on how you coded things.

Chip H.




____________________________________________________________________
If you want to get the best response to a question, please read FAQ222-2244 first

 

[chiph]

obislavu has a good example of using BeginInvoke at thread732-868602

Chip H.


____________________________________________________________________
If you want to get the best response to a question, please read FAQ222-2244 first

 

[brentnewbury]

Thank you both for your replies,

I did look at Thread732-868602, but it didn't seem to make much sense to me. I tried looking for delegates and other things but never, did a search for BeginInvoke(). Oh well.

Thank you both.

Brent

 

[brentnewbury]

For anyone else who comes across this problem, here are a few links that helped me:

http://msdn.microsoft.com/library/d...html/vbtskmanipulatingcontrolsfromthreads.asp

http://msdn.microsoft.com/library/d...gsimplemultithreadedcomponenetwithvisualc.asp

Thank you all for all your help.


Brent