Linq join 3 list <T>

本文关键字：gt join lt list Linq | 更新日期: 2023-09-27 18:02:48

我有三个列表需要连接在一起

class Person
{
    public int PersonID{ get; set; }
    public string FirstName{get; set;}
    public string LastName {get; set;}
}
class Traffic
{
    public DateTime Date{ get; set; }
    public int PersonID;
    public int TrafficID;
}
class TrafficType
{
    public int TrafficID { get; set; }
    public string Description  { get; set; }
}
List<Person> Persons=GetPersons();
List<TrafficType> TrafficTypes=GetTrafficTypes();
List<Traffic> Traffics=GetTraffics();

我需要这样的输出:

<>之前PersonID FirstName LastName Date描述大卫……2011/07/19样品描述

Linq join 3 list <T>

from person in Persons
from traffic in traffics
from trafficType in trafficTypes
where trafficType.TrafficID = traffic.TrafficID 
where traffic.PersonID = person.PersonID
select new 
{
    PersonID = person.PersonID,
    ....
}

var result = Persons.Join(
    Traffics,
    person => person.PersonID,
    trafic => trafic.PersonID,
    (person, trafic) => new
    {
        PersonId = person.PersonID,
        FirstName = person.FirstName,
        LastName = person.LastName,
        Date = trafic.Date,
        TraficId = trafic.TrafficID
    }).Join(
        TrafficTypes,
        a => a.TraficId,
        traficType => traficType.TrafficID,
        (a, traficType) => new
        {
            PersonId = a.PersonId,
            FirstName = a.FirstName,
            LastName = a.LastName,
            Date = a.Date,
            Description = traficType.Description
        });

下面是一个完整的Linq查询表达式代码示例，它应该得到你正在寻找的东西:

using System;
using System.Collections.Generic;
using System.Linq;
class Person
{
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
}
class Traffic
{
    public DateTime Date { get; set; }
    public int PersonId { get; set; }
    public int TrafficId { get; set; }
}
class TrafficType
{
    public int Id { get; set; }
    public string Description { get; set; }
}
class Program
{
    static void Main(string[] args)
    {
        var persons = new List<Person>()
        {
            new Person()
            {
                Id = 1001,
                FirstName = "David",
                LastName = "Jones",
            },
        };
        var trafficTypes = new List<TrafficType>()
        {
            new TrafficType()
            {
                Id = 456,
                Description = "sample description",
            },
        };
        var traffics = new List<Traffic>()
        {
            new Traffic()
            {
                PersonId = 1001,
                TrafficId = 456,
                Date = DateTime.Now,
            },
        };
        var joinedData = from p in persons
                         from t in traffics
                         from tt in trafficTypes
                         where p.Id == t.PersonId
                            && tt.Id == t.TrafficId
                         select new
                         {
                             PersonId = p.Id,
                             FirstName = p.FirstName,
                             LastName = p.LastName,
                             // Remove time component, if present
                             Date = t.Date.Date,
                             Description = tt.Description,
                         };
        foreach (var item in joinedData)
        {
            Console.WriteLine("{0}'t{1}'t{2}'t{3}'t{4}"
                , item.PersonId
                , item.FirstName
                , item.LastName
                , item.Date.ToShortDateString() // Don't print the time
                , item.Description
                );
        }
    }
}

程序输出为:

1001    David   Jones   7/19/2011       sample description

你可以把它们都放在一个类中，例如(Problem)，然后使用一个方法输出。

class Problem
{
   public Problem()
   {
   }
   public void Show()
   {
         // implement your output here
   }
}

或者，如果你正在使用Windows窗体应用程序和感兴趣的表，你可以使用DataGridView控件。更多信息，请访问http://msdn.microsoft.com/en-us/library/e0ywh3cz.aspx

或者使用DataGrid: http://www.codeproject.com/KB/grid/usingdatagrid.aspx

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