C#

public class MyClass
{
   public delegate void LiveStatsLoginRequest(object sender, LiveStatsLoginEventArgs e);
   public event LiveStatsLoginRequest OnLSLoginRequest;

   public MyClass()
   {

   }

   public void OpenConnection(string postData)
   { 
      var args = new object[] {postData, Operation.Check, LiveStatsAction.Authenticate};
      var t = new Thread(dowork);
      t.Start(args);
   }

   private void dowork(object args)
   {
      DoSomethingThatTakesALongTime();
      OnLSLoginRequest.Invoke(this, new EventArgs());
   }
}

public partial class MainForm : Form
{
   private MyClass myClass;

   public MainForm()
   {
      InitializeComponent();
      myClass = new MyClass();
      MyClass.OnLSLoginRequest += LiveStats_OnLSLoginRequest;
   }

   private void Form_Load(object sender, EventArgs e)
   {
      myClass.OpenConnection(new object[]{"Something"};
   }

   private void LiveStats_OnLSLoginRequest(object sender, LiveStatsLoginEventArgs e)
   {
       this.TextBox1.Text = "Logged in!";
   }
}

private void LiveStats_OnLSLoginRequest(object sender, LiveStatsLoginEventArgs e)
{
    if (InvokeRequired)
    {
        //do invoke
    }
    else
    {
        this.TextBox1.Text = "Logged in!";
    }
}