Question

我试图根据某些条件过滤对象列表。我已经看到一些帖子在他们的LINQ查询中使用三元运算符来完成此任务。

在此代码段的底部是我的LINQ查询。我希望它能够测试每个where，而只是尝试第一个where并留下其余部分。 List不包含我期望的数据。我做错了什么？

    private ObservableCollection<LogEvent> m_LogEvents = ApplicationData.MainLogEntries.LogEvents;
    public ObservableCollection<LogEvent> LogEvents
    {
        get { return m_LogEvents; }
        set { m_LogEvents = value; RaisePropertyChanged("LogEvents"); }
    }

    private bool m_ViewDebugLogs = false;
    public bool ViewDebugLogs
    {
        get { return m_ViewDebugLogs; }
        set { m_ViewDebugLogs = value; RaisePropertyChanged("ViewDebugLogs"); FilterList(); }
    }

    private bool m_ViewErrorLogs = true;
    public bool ViewErrorLogs
    {
        get { return m_ViewErrorLogs; }
        set { m_ViewErrorLogs = value; RaisePropertyChanged("ViewErrorLogs"); FilterList(); }
    }

    private bool m_ViewInfoLogs = true;
    public bool ViewInfoLogs
    {
        get { return m_ViewInfoLogs; }
        set { m_ViewInfoLogs = value; RaisePropertyChanged("ViewInfoLogs"); FilterList(); }
    }

    private void FilterList()
    {
        List<LogEvent> selectedEvents = (from x in LogEvents
                                         where (ViewDebugLogs) ? x.Level == "Debug" : false
                                         where (ViewErrorLogs) ? x.Level == "Error" : false
                                         where (ViewInfoLogs) ? x.Level == "Info" : false
                                         select x).ToList();

    }

编辑：这样做的目的是，如果启用了适当的bool ViewDebugLogs，ViewErrorLogs或ViewInfoLogs或这三者的任意组合，则会按适当的类型过滤日志。

我从答案中尝试了以下内容但没有成功：

仅获得Debug Logs：

            List<LogEvent> selectedEvents = (from x in LogEvents
                                         where (ViewDebugLogs == true) ? x.Level == "Debug" : false
                                         || (ViewErrorLogs == true) ? x.Level == "Error" : false
                                         || (ViewInfoLogs == true) ? x.Level == "Info" : false
                                         select x).ToList();

仅获得Debug Logs：

            List<LogEvent> selectedEvents = (from x in LogEvents
                                         where (ViewDebugLogs == true) ? x.Level == "Debug" : true
                                         || (ViewErrorLogs == true) ? x.Level == "Error" : true
                                         || (ViewInfoLogs == true) ? x.Level == "Info" : true
                                         select x).ToList();

这没有任何结果：

            List<LogEvent> selectedEvents = (from x in LogEvents
                                         where (ViewDebugLogs == true) ? x.Level == "Debug" : true
                                         where (ViewErrorLogs == true) ? x.Level == "Error" : true
                                         where (ViewInfoLogs == true) ? x.Level == "Info" : true
                                         select x).ToList();

Answer 1

多个where条件被连接，就像您使用AND一样。如果您尝试OR，则应使用||代替。

List<LogEvent> selectedEvents = (from x in LogEvents
                                 where (ViewDebugLogs) ? x.Level == "Debug" : false
                                 || (ViewErrorLogs) ? x.Level == "Error" : false
                                 || (ViewInfoLogs) ? x.Level == "Info" : false
                                 select x).ToList();

Answer 2

您可以使用

 List<LogEvent> selectedEvents = (from x in LogEvents
                           where (ViewDebugLogs && x.Level == "Debug") 
                              || (ViewErrorLogs && x.Level == "Error")
                              || (ViewInfoLogs  && x.Level == "Info") 
                           select x).ToList();

这更清楚（在我看来）。请注意表达式部分周围的( )：我想确定评估AND和OR的顺序。

Answer 3

Where子句可以是where (ViewDebugLogs) ? x.Level == "Debug" : ((ViewErrorLogs) ? x.Level == "Error" : ((ViewInfoLogs) ? x.Level == "Info" : false))

LINQ查询中的三元运算符未按预期工作

3 个答案: