需要有关开发LINQ Lambda表达式以过滤计划的帮助

Question

我很难找到要在列表上调用的lambda表达式来正确过滤对象结构。我希望有人可以提供帮助。我使用的是.NET 3.5，LINQ和对象域是从Linq到SQL DBML设置的。我特别想使用 lambda表达式。

对象结构是人员具有设置的对象结构，其中一个设置是计划名称，对应于具有StartDate和结束日期的另一个计划类。

public class MyPerson
{
    public int ID { get; set; }
    public List<MySetting> Settings { get; set; }
}

public class MySetting
{
    public int ID { get; set; }
    public string Name { get; set; }
    public string Value { get; set; }
}

public class MySchedule
{
    public string ID { get; set; }
    public DateTime StartDate { get; set; }
    public DateTime EndDate { get; set; }

}

计划具有开始日期和结束日期，并且人员的状态可以是活动的或计划的。

    List<MySchedule> schedules = new List<MySchedule>();
    MySchedule scheduleA = new MySchedule { ID = "ScheduleA", StartDate = Convert.ToDateTime("1/1/2008"), EndDate = Convert.ToDateTime("12/31/2008") };
    MySchedule scheduleB = new MySchedule { ID = "ScheduleB", StartDate = Convert.ToDateTime("1/1/2009"), EndDate = Convert.ToDateTime("12/31/2009") };
    schedules.Add(scheduleA);
    schedules.Add(scheduleB);

    List<MySetting> settingsJill = new List<MySetting>();
    MySetting settingFirstName = new MySetting { ID = 1, Name = "FirstName", Value = "Jill" };
    MySetting settingScheduleName = new MySetting { ID = 2, Name = "ScheduleName", Value = "ScheduleB" };
    MySetting settingState = new MySetting { ID = 3, Name = "State", Value = "Scheduled" };  // Jill uses ScheduleB
    settingsJill.Add(settingFirstName);
    settingsJill.Add(settingScheduleName);
    settingsJill.Add(settingState);

    List<MySetting> settingsBill = new List<MySetting>();
    settingFirstName = new MySetting { ID = 1, Name = "FirstName", Value = "Bill" };
    settingScheduleName = new MySetting { ID = 2, Name = "ScheduleName", Value = "ScheduleA" };
    settingState = new MySetting { ID = 3, Name = "State", Value = "Scheduled" };              // Bill is Scheduled last year
    settingsBill.Add(settingFirstName);
    settingsBill.Add(settingScheduleName);
    settingsBill.Add(settingState);

    List<MySetting> settingsJane = new List<MySetting>();
    settingFirstName = new MySetting { ID = 1, Name = "FirstName", Value = "Jane" };
    settingScheduleName = new MySetting { ID = 2, Name = "ScheduleName", Value = "ScheduleA" };
    settingState = new MySetting { ID = 3, Name = "State", Value = "Active" };              // Jane is Active
    settingsJane.Add(settingFirstName);
    settingsJane.Add(settingScheduleName);
    settingsJane.Add(settingState);

    List<MyPerson> persons = new List<MyPerson>();
    MyPerson Jane = new MyPerson { ID = 1, Settings = settingsJane };
    MyPerson Jill = new MyPerson { ID = 2, Settings = settingsJill };
    persons.Add(Jane);
    persons.Add(Jill);
    persons.Add(Bill);

我想通过创建一个lambda表达式来过滤人员List，该表达式将返回State =＆quot; Active＆quot;或者包含ScheduleName，其中包含开始日期和结束日期之间的当前日期。换句话说，Jill应该出现在已过滤的列表中，因为她是Scheduled，她使用ScheduleB，ScheduleB是2009年，今天是6/17/2009。

我从

开始

List<MyPerson> filter = persons.Select (  // and this is where I get stuck.

提前感谢您的帮助。

Answer 1

您需要重新考虑如何存储信息。 .NET Collectionns不是SQL表，您不应该像这样使用它们。话虽如此，这是您想要的查询：

Persons.Where(person => 
  person.Settings.Any(setting=>
      (setting.Name == "State" && setting.Value=="Active")) ||
  person.Settings
      .Where(setting=> setting.Name == "ScheduleName")
      .Any(setting => { var sch = schedules
           .First(schedule=>schedule.ID == setting.Value);
           return sch.StartDate < DateTime.Now && sch.EndDate > DateTime.Now; 
      })   
)

想象一下，如果你有一个像：

这样的数据结构

class Person { 
    Dictionary<string, string> Settings;
    List<MySchedule> Schedules;
}

then your query would be

Persons.Where(person =>
   Person.Settings["State"] == "Active" ||
   Person.Schedules.Any(schedule => 
       Datetime.Now > schedule.StartTime &&
       DateTime.Now < schedule.EndTime
   )
)

Answer 2

一个问题是你开始使用选择。这是投影 - 你只是想过滤，所以你只需要 Where 。

另一个问题是您的 MyPerson 类型不包含 ScheduleName 或 State 属性。目前尚不清楚它是如何挂在一起的。如果你能纠正你的例子，我相信我们可以拿出过滤器。