public DateTime? LastLoginDate { get { return this.lastLoginDate; } set { this.lastLoginDate = value; } }
lblLastLoginDate.Text = "最后登录:" + ((DateTime)LoginUserInfo.LastLoginDate).ToString("f"); // 可为空的对象必须具有一个值
LoginUserInfo.LastLoginDate.HasValue ? LoginUserInfo.LastLoginDate.Value : DateTime.Now