C#

private void SetImageLocation(string uri)
{
  if (pictureBox1.InvokeRequired)
  {
    Action<string> setImageLocation = SetImageLocation;
    pictureBox1.Invoke(setImageLocation, new object[] { uri });
  }
  else
  {
    pictureBox1.ImageLocation = uri;
  }
}

private void DoWork()
{
  for (int i = 0; i < 20000; ++i)
  {
    if (i == 5000)
    {
      SetImageLocation("x.gif");
    }
  }
}

// Assumes you're executing work in response to a Button.Click event.
private void button1_Click(object sender, EventArgs e)
{
  ThreadPool.QueueUserWorkItem(DoWork);
}

int i = 0;
            while (i<2000000000)
            {
                if (i==5000) {
                    pictureBox1.Load("x.gif");

                    Application.DoEvents();

                }
                
                i++;
            }

abdellah ab wrote:

if (i=5000) {

internal abstract class MyFormBase : Form
{
  DataGridView dataGridView1;

  protected MyFormBase()
  {
    dataGridView1 = new DataGridView();
    dataGridView1.CellClick += OnDataGridViewCellClick;
    // Other initialization
  }

  protected virtual string Message
  {
    get { return "Message from the base class."; }
  }

  protected virtual void OnDataGridViewCellClick(object sender, DataGridViewCellEventArgs e)
  {
    // Override this in your child class if you wish.
  }

  protected virtual void OnDataGridViewColumnHeaderMouseClick(object sender, DataGridViewBindingCompleteEventArgs e)
  {
    MessageBox.Show(Message, "Test");
  }
}

internal class MyChildForm : MyFormBase
{
  protected override string Message
  {
    get { return "Message from the child class."; }
  }

  protected override void OnDataGridViewCellClick(object sender, DataGridViewCellEventArgs e)
  {
    MessageBox.Show("You clicked a cell.", "Test");

    // Example of how to call a base method. Not always required, and in this case doesn't do anyway.
    // However, for some virtual methods it's very important to call the base so read documentation.
    base.OnDataGridViewCellClick(sender, e);
  }
}

private abstract void OnDataGridViewCellClick(object sender, DataGridViewCellEventArgs e);