Dealing with controls within a multi threaded context

Many people don't pay attention to the fact that controls couldn't be directly invoked within a thread context other than the one within which they have been created. And then their applications fall down because a run time error will be raised when firing the application. It is technically called none valid cross thread operation. It generates an InvalidOperationException.

As explanation to this error, I can say that each thread has its proper boundary exactly like a state that has a boundary. And it is not legal to travel from a county to another one without achieving some administrative tasks. It is exactly the same fact from an analogical point of view.

Therefore, it is not possible for a control that has been created within a given thread to be directly used within another thread event when one try to avoid the problem by using a Backgroundworker he/she won't resolve the problem if he/she doesn't have a complete idea about dealing with controls and or objects within a multithreaded contexts.

There are many used techniques in order to resolve the problem and I will represent one of those techniques.
But first let's see what will happen when an invalid cross threaded operation is designed and tested:

First, create a new windows application project and add a progress bar, a button and a label into the form1 so that it appears as under:

Add the namespace

using System.Threading;

Then try this code

public partial class Form1 : Form
{

Thread myThread;
public Form1()
{
InitializeComponent();

myThread = new Thread(new ThreadStart(ModifyControlsState));
}

public void ModifyControlsState()
{
progressBar1.Minimum = 0;
progressBar1.Maximum = 100;
for (int i = 0; i <= 100; i = i + 1)
{
progressBar1.Increment(i);
label1.Text = progressBar1.Value.ToString() + "%omplete"; Thread.Sleep(10);
}
DialogResult dlg = MessageBox.Show("Do you want to close this window",
"Do you want to exit this window",
MessageBoxButtons.OKCancel);
if (dlg == DialogResult.OK) Application.Exit(); }