private void dgvUsers_DoubleClick(object sender, EventArgs e)
        {
            int UserID;

            if (WinFormUtil.DataGridView_GetSelectedID(dgvUsers, out UserID))
            {
                BOUser   current_user = AccountantPool.Instance.CurrentAccountant.User;
                AuthUser user         = current_user.GetAuthUser(UserID);
                if (user != null)
                {
                    FrmAuthUser frm = new FrmAuthUser();
                    frm.Username    = user.Username;
                    frm.Password    = user.Password;
                    frm.Role        = user.Role;
                    frm.Description = user.Description;
                    if (frm.ShowDialog() == DialogResult.OK)
                    {
                        user.Username    = frm.Username;
                        user.Password    = frm.Password;
                        user.Description = frm.Description;
                        user.Role        = frm.Role;
                        current_user.SaveAuthUser(user);
                        ViewModel();
                    }
                }
            }
        }
        private void btnCreateUser_Click(object sender, EventArgs e)
        {
            FrmAuthUser frm = new FrmAuthUser();

            if (frm.ShowDialog() == DialogResult.OK)
            {
                AuthUser user = AuthUser.CreateAuthUser();

                user.Username    = frm.Username;
                user.Password    = frm.Password;
                user.Description = frm.Description;
                user.Role        = frm.Role;

                BOUser current_user = AccountantPool.Instance.CurrentAccountant.User;
                current_user.SaveAuthUser(user);

                ViewModel();
            }
        }