检索除一个数据库之外的清单

Question

您有一个很大的列表，目标是检索下面的新列表

今天：

number   color   brand   size   tiresize
-----------------------------------------
1         blue   d       5      6
2         blue   d       5      6
3         red    b       3      3
4         red    b       3      3
etc....

目标：

number   color   brand   size   tiresize
-----------------------------------------
          blue   d       5      6
          red    b       3      3

目标是检索区分的列表并删除“数字”。

这个样本很小，实际上该列表大约有26个数据库。

我正在考虑使用distinct（），但它会考虑到所有数据，并且我不想考虑到“数字”列

当您检索新列表时，请求之前使用相同的类与区别列表。

public Car
{
    public int number
    public string color
    public string brand
    public string size
    public string tiresize
}

谢谢！

Answer 1

var cars = new List<Car>
{
   new Car{number = 1, color="blue", brand="d", size = "5", tiresize = "6"},
   new Car{number = 2, color="blue", brand="d", size = "5", tiresize = "6"},
   new Car{number = 3, color="red", brand="b", size = "3", tiresize = "3"},
   new Car{number = 4, color="red", brand="b", size = "3", tiresize = "3"},
};

var distinctCars = cars.GroupBy(x => new {x.color, x.brand, x.size, x.tiresize});                

foreach (var car in distinctCars)
{
   Console.WriteLine(car.Key.color +  ": " + car.Key.brand +  ": " + car.Key.size +  ": " + car.Key.tiresize);
} 

Answer 2

一种方法，使用匿名类型，它具有内置Equals + GetHashCode实现，可比较所有属性：

var distinctCars = cars
    .Select(c => new {c.color, c.brand, c.size, c.tiresize})
    .Distinct()
    .Select(x => new Car {color = x.color, brand = x.brand, size = x.size, tiresize = x.tiresize})
    .ToList(();

其他方式是

1. 自己在Equals覆盖GetHashCode + Car
   • 也可以选择实施IEquatable<Car>
2. 提供您可以在IEqualityComparer<Car>
中使用的自定义Distinct