Question

要把它归结为黄铜钉，我有一个包含100种不同记录的列表。汽车有年，制造和模型。

我需要能够：

按照年份订购，但我需要：
拥有所有福特汽车探险家作为一个“团体”出现在我的清单结束（也订购了根据年份）

我不确定我是否必须创建2个单独的List然后合并它们......似乎应该有一个更好的方法来做到这一点，而不是必须创建多个对象。

感谢您的帮助！

非常感谢，保罗

示例：

2001悍马H1
2002福特福克斯2008 2008宝马325i
2008福特Escape
2009 BMW 328i
2009 2009三菱Galant < br /> 2003年福特资源管理器
2004年福特资产管理器
2008福特资产管理器
2009福特资产管理器

车轮

Answer 1

如果您真的只想将福特探险家分组，您可以执行以下操作：

var groupedByFordExplorer = from c in cars
                    let isFordExplorer = c.Make == "Ford" && c.Model == "Explorer"
                    orderby isFordExplorer, c.Year
                    select c;

上述查询的作用是创建一个内联值isFordExplorer，并使用let关键字为其指定一个布尔值，指示该车是否为福特资源管理器。然后可以将该值与年份一起排序。以下是一个应该展示这个概念的工作程序：

class Program
{
    static void Main(string[] args)
    {
        var cars = new List<Car>
        {
            new Car { Year = 2009, Make = "Ford", Model = "Explorer" },
            new Car { Year = 2001, Make = "Hummer", Model = "H1" },             
            new Car { Year = 2002, Make = "Ford", Model = "Focus" },
            new Car { Year = 2008, Make = "BMW", Model = "325i" },
            new Car { Year = 2008, Make = "Ford", Model = "Explorer" },             
            new Car { Year = 2008, Make = "Ford", Model = "Escape" },               
            new Car { Year = 2009, Make = "Mitsubishi", Model = "Galant" },
            new Car { Year = 2004, Make = "Ford", Model = "Explorer" },
            new Car { Year = 2009, Make = "BMW", Model = "329i" },
            new Car { Year = 2003, Make = "Ford", Model = "Explorer" }              
        };

        var groupedByFordExplorer = from c in cars
                                    let isFordExplorer = c.Make == "Ford" && c.Model == "Explorer"
                                    orderby isFordExplorer, c.Year
                                    select c;

        foreach (var car in groupedByFordExplorer)
        {
            Console.WriteLine("{0} {1} {2}", car.Year, car.Make, car.Model);
        }

        Console.ReadLine();
    }
}

class Car
{
    public int Year { get; set; }
    public string Make { get; set; }
    public string Model { get; set; }
}

Answer 2

这应该这样做：

var query = list.OrderBy(car => car.Make == "Ford" && car.Model == "Explorer")
                .ThenBy(car => car.Year);

（显然调整了对福特Explorer的测试。）

基本上将Ford Explorer-ness视为布尔属性，其中false在true之前排序。当然，您也可以将其表达为查询表达式：

var query = from car in list
            orderby car.Make == "Ford" && car.Model == "Explorer", car.Year
            select car;

（在这种情况下，我倾向于使用点符号。）

Answer 3

cars.OrderBy(c => 
        (c.Make == "Ford" && c.Model == "Explorer")
        ? c.Year + 10000
        : c.Year)
    .ToList()

考虑下面我的评论，如果是LINQ to sql，我可能会用联盟写一下：

cars.Where(c => c.Make != "Ford" || c.Model != "Explorer")
    .OrderBy(c => c.Year)
    .Union(cars.Where(c => c.Make == "Ford" && c.Model == "Explorer")
               .OrderBy(c => c.Year))

C＃LINQ计算Group By

3 个答案: