private void LoginForm_VisibleChanged(object sender, EventArgs e)
 {
     if (this.Visible)
     {
         TebPassword.Focus();
     }
 }
        private void BtnLogin_Click(object sender, EventArgs e)
        {
            //获取用户名和密码
            UserMode user     = (UserMode)Enum.Parse(typeof(UserMode), CobUser.Text);
            string   password = TebPassword.Text;

            TebPassword.Clear();

            if (UserChangingMethod != null)
            {
                //切换用户,返回切换后的用户
                bool result = UserChangingMethod(user, password);
                if (result)
                {
                    if (user == UserMode.Manager)
                    {
                        BtnManaMode.BaseColor  = BtnManaMode.BaseColorEnd = Color.FromArgb(4, 86, 240);
                        BtnOperaMode.BaseColor = BtnManaMode.BaseColorEnd = Color.Transparent;
                    }
                    else
                    {
                        BtnManaMode.BaseColor  = BtnManaMode.BaseColorEnd = Color.Transparent;
                        BtnOperaMode.BaseColor = BtnManaMode.BaseColorEnd = Color.FromArgb(4, 86, 240);
                    }
                }
            }
        }
 private void CobUser_SelectedIndexChanged(object sender, EventArgs e)
 {
     TebPassword.Focus();
 }