Winform程序实现系统登入/登出功能

private void btnLogin_Click(object sender, EventArgs e)
{
   try
   {
      this.SuspendLayout();
      this.Cursor = Cursors.WaitCursor;
      SetButtonEnable(false);
      
      //调用业务层登录方法
      Loginer ret = new bllUser().Login(txtUser.Text,txtPwd.Text);
      
      if (ret != null)
      {
         Loginer.CurrentUser = ret;//保存当前用户
         
         if (AppEntry.MainForm == null)
         {
            //登录成功创建主窗体
            AppEntry.MainForm = new frmMain();
         }

         //初始化主窗体(如加载模块，初始化用户界，加载系统参数)
         //在初始化同时login窗体会动态显示信息。
         AppEntry.MainForm.InitUserInterface(new StatusLable(this.lblLoadingInfo));
         
         this.DialogResult = DialogResult.OK;
         this.Close(); //关闭登陆窗体
      }
      else
      {
         Msg.Warning("登录失败，请检查用户名和密码!");
      }
   }
   catch (Exception ex)
   {
      Msg.Warning("登录失败，请检查用户名和密码!");
      this.Cursor = Cursors.Default;
      
   }
   finally
   {
      this.Cursor = Cursors.Default;
      SetButtonEnable(true);
      this.ResumeLayout();
   }
}

private void btnLogout_Click(object sender, EventArgs e)
{
   if (!Msg.AskQuestion("真的要登出吗?")) return;
   try
   {
      if (this.DataChanged())
      {
         Msg.Warning("系统检测到有数据窗体没有保存，不能登出!");
         return;
      }
      
      if (!Application.AllowQuit) return;
      
      this.Hide();
      
      AppEntry.MainForm = null;
      if (AppEntry.Login() && AppEntry.MainForm != null)
      AppEntry.MainForm.Show();
      
      GC.Collect();
   }
   catch (Exception ex)
   { Msg.ShowException(ex); }
   
}

static class Program
{
   [STAThread]
   static void Main()
   {
      //捕获系统所产生的异常。
      Application.ThreadException += new ThreadExceptionEventHandler(Application_ThreadException);
      
      //注册Dev Express皮肤
      DevExpress.UserSkins.BonusSkins.Register();
      DevExpress.UserSkins.OfficeSkins.Register();
      DevExpress.Skins.SkinManager.EnableFormSkins();
      
      Application.EnableVisualStyles();
      Application.SetCompatibleTextRenderingDefault(false);
      
      //注意：先打开登陆窗体,如登陆成功后再正式运行程序(MDI 主窗体)
      if (AppEntry.Login())
      {
         AppEntry.MainForm.Show();
         Application.Run();
      }
      else
      Application.Exit();
   }
   
   private static void Application_ThreadException(object sender, ThreadExceptionEventArgs e)
   {
      Msg.ShowException(e.Exception);
   }
}