C#

// Waiting for 'Account in use' and 'Register success or failure'
AutoResetEvent[] loginWaitEvents = new AutoResetEvent[]
{
            new AutoResetEvent(false), 
            new AutoResetEvent(false)
};

private void bgwProcessLogin_DoWork(object sender, DoWorkEventArgs e)
{
          Console.WriteLine("Wait until event is set or timeout");
          loginWaitEvents[0].WaitOne(3000, true);
          
          if (this.accountInUseFlag)
          {
                    if (this.lblRegistering.InvokeRequired)
                    {
                        this.lblRegistering.Invoke(new UpdateRegisterLabelDelegate(this.UpdateRegisterLabel), "Account in use");
                    }
                    else
                    {
                        this.lblRegistering.Text = "Account in use";
                    }
                    // Failed attemp
                    e.Cancel = true;
                    // Reset flag
                    this.accountInUseFlag = false;
                    return;
           }
           else
           {
                    // Report current progress
                    this.bgwProcessLogin.ReportProgress(7, "Account accepted");
           }

            Console.WriteLine("Just Wait the result of successfull login or not");
            loginWaitEvents[1].WaitOne();
           
            if (this.registerSuccess)
            {
                    // Report current progress
                    this.bgwProcessLogin.ReportProgress(7, "Register Succesfull");  
                    // Reset flag
                    this.registerSuccess = false;
            }
            else
            {
                    if (this.lblRegistering.InvokeRequired)
                    {
                        this.lblRegistering.Invoke(new UpdateRegisterLabelDelegate(this.UpdateRegisterLabel), "Failed to register");
                    }
                    else
                    {
                        this.lblRegistering.Text = "Failed to register";
                    }
                    // Failed attemp
                    e.Cancel = true;               
                    return;   
            }
}

// Wait for the callback to set the AutoResetEvent

// Error sometimes happens when the function leaves scope.
private void VaxSIPUserAgentOCX_OnSuccessToRegister(object sender, EventArgs e)
{
            Console.WriteLine("OnSuccessToRegister() [ Registered successfully ]");
            this.registerSuccess = true;
            this.loginWaitEvents[1].Set();
} 


// If the flag is not set, then just time out after 3 seconds for the first LoginWaitEvent.waitOne(3000, true)
 private void VaxSIPUserAgentOCX_OnIncomingDiagnostic(object sender, AxVAXSIPUSERAGENTOCXLib._DVaxSIPUserAgentOCXEvents_OnIncomingDiagnosticEvent e)
{
            string messageSip = e.msgSIP;

            //Indicates that a user is already logged on (Accout in use).
            string sipErrorCode = "600 User Found"; 
            if (messageSip.Contains(sipErrorCode))
            {
                // Set flag for account in use
                this.accountInUseFlag = true;
                Console.WriteLine("OnIncomingDiagnostic() WaitEvent.Set() accountInUseFlag: " + this.accountInUseFlag);
                loginWaitEvents[0].Set();   
            }
}