C#

foreach(Control subControl in myForm.Controls)
{
    subControl.Text = "Howdy!";
}

SetSubControlText(Control ctrl, string text)
{
    if(ctrl.Controls.Count > 0)
    {
        foreach(Control subControl in ctrl.Controls)
        {
           subControl.Text = text;
           SetSubControlText(subControl);
        }
    }
}

if (control.InvokeRequired)
  control.Invoke(...., .....);
else
  //call function normally

class CA : System.Windows.Forms.Form
{
    ...
    
    protected void OnMyEvent(int nCount)
    {
        if (this.InvokeRequired)
        {
            // Marshal the call to the correct thread:
            this.Invoke(new OnMyEventHandler(this.OnMyEvent));
        }
        else
        {
            for ( int i = 0; i < nCount; i ++ )
            {
                Button btn = new Button();
                btn.Parent = this; 
                btn.Location = new Point( 100 + i * 100, 10 );
                btn.Show();
            }
        }
    }
}