//Event handler for Sign-In/Sign-Out button clicks.
        private void buttonSignInOrOut_Click(object sender, EventArgs e)
        {
            //Check to see if the user is not currently authenticated.
            if (!oID.IsAuthenticated)
            {
                try
                {
                    //Try to authenticate the user by showing the Sign-In dialog window.
                    if (oID.Authenticate())
                    {
                        currentUserName = oID.UserName;
                    }
                    else
                    {
                        MessageBox.Show("Authentication failed");
                    }
                }
                catch (WLLogOnException wlex)
                {
                    //Check to see if FlowUrl is defined.
                    if (wlex.FlowUrl != null)
                    {
                        //If FlowUrl is defined, direct user to the web page to correct the error.
                        MessageBox.Show(wlex.ErrorString + "Please go to " + wlex.FlowUrl.AbsoluteUri + "to correct the condition that caused the error");
                    }
                    else
                    {
                        //If FlowUrl is not defined, simply display the ErrorString.
                        MessageBox.Show(wlex.ErrorString);
                    }
                }
            }
            else
            {
                //If user is authenticated, they intended to Sign-Out. Try signing the user out.
                try
                {
                    oID.CloseIdentityHandle();
                    currentUserName = "";
                }
                catch (WLLogOnException wlex)
                {
                    //Check to see if FlowUrl is defined.
                    if (wlex.FlowUrl != null)
                    {
                        //If FlowUrl is defined, direct user to the web page to correct the error.
                        MessageBox.Show(wlex.ErrorString + "Please go to " + wlex.FlowUrl.AbsoluteUri + "to correct the condition that caused the error");
                    }
                    else
                    {
                        //If FlowUrl is not defined, simply display the ErrorString.
                        MessageBox.Show(wlex.ErrorString);
                    }
                }
            }
            UpdateDisplay();
        }