我有两个模型：

public class CarRent
{
    public string CarName { get; set; }
    public string SystemId { get; set; }
    public DateTime RentEndDate { get; set; }
}

public class CarPurchase
{
    public string CarName { get; set; }
    public string SystemId { get; set; }
    public decimal Mileage { get; set; }
}

我需要将它们组合到一个列表中,按CarName分组,然后在每个组中首先需要按SystemId排序模型,但是如果模型具有相同的SystemId-我需要按RentEndDate排序CarRent模型,按Mileage排序CarPurchase.

我尝试过的

我定义了一个接口：

public interface ICarPurchaseOrdered
{
    string CarName { get; }
    string SystemId { get; }
    string Order { get; }
}

并让我的模型来实现它,Order属性仅返回二阶条件的字符串表示形式,然后定义了一个视图模型：

public class GroupedCardList
{
    public string CarName { get; set; }
    public IEnumerable<ICarPurchaseOrdered> Cars { get; set; }
}

然后我有一个将我的模型分组的石斑鱼：

public class CarGrouper
{
    IEnumerable<GroupedCardList> Group(IEnumerable<ICarPurchaseOrdered> cars)
    {
        return cars.GroupBy(c => c.CarName)
                   .OrderBy(c => c.Key)
                   .Select(c => new GroupedCardList()
                   {
                       CarName = c.Key,
                       Cars = c.OrderBy(n => n.SystemId)
                               .ThenBy(n => n.Order)
                   });
    }
}

但这行不通,因为它会对字符串进行排序,而我在购买Milage = 90的汽车之前先购买Milage = 1200的汽车.

我知道这个例子有些人为,但这完全代表了我现在遇到的问题.请给我一些建议.

解决方法:

一种方法是实现自定义IComparer.如果提取公共基类：

public class Car
{
    public string CarName { get; set; }
    public string SystemId { get; set; }
}

public class CarRent : Car
{
    public DateTime RentEndDate { get; set; }
}

public class CarPurchase : Car
{
    public decimal Mileage { get; set; }
}

然后,将IComparer< Car>实现可能如下所示：

public class CarComparer : IComparer<Car>
{
    public int Compare(Car x, Car y)
    {
        // compare by system id first
        var order = string.Compare(x.SystemId, y.SystemId);
        if (order != 0)
            return order;

        // try to cast both items as CarRent
        var xRent = x as CarRent;
        var yRent = y as CarRent;
        if (xRent != null && yRent != null)
            return DateTime.Compare(xRent.RentEndDate, yRent.RentEndDate);

        // try to cast both items as CarPurchase
        var xPurc = x as CarPurchase;
        var yPurc = y as CarPurchase;
        if (xPurc != null && yPurc != null)
            return decimal.Compare(xPurc.Mileage, yPurc.Mileage);

        // now, this is awkward
        return 0;
    }
}

然后,您可以将比较器实例传递给List.Sort和Enumerable.OrderBy.