为什么我的 if 语法在这些条件下不起作用？

Question

{
    _cars = new List<Car> 
                {
                    new Car { Id = 1, BrandId = 1, ColorId = 13, DailyPrice = 30000, Description = "BMW 5.20", ModelYear = 2023, BrandName = "BMW" },
                    new Car { Id = 2, BrandId = 1, ColorId = 13, DailyPrice = 5, Description = "BMW 5.20", ModelYear = 2023, BrandName = "B" },
                    new Car { Id = 3, BrandId = 3, ColorId = 10, DailyPrice = 25000, Description = "Mercedes C180", ModelYear = 2023, BrandName = "Mercedes" },
                    new Car { Id = 4, BrandId = 5, ColorId = 11, DailyPrice = 21000, Description = "Hyundai i20n", ModelYear = 2023, BrandName = "BMW" },
                    new Car { Id = 5, BrandId = 3, ColorId = 10, DailyPrice = 40000, Description = "Mercedes A180", ModelYear = 2023, BrandName = "Mercedes" },
                };
}

public void Add(Car car)
{
    if (car.DailyPrice > 10 && car.BrandName.Length > 2)
    {
         _cars.Add(car);
    }
    else 
    {
         Console.WriteLine("Error");
    }
}

我应该第二次收到错误消息

new car(id2)

。但我没有看到任何错误，它确实有效，并且我可以在我的控制台上看到它。

我在这里做错了什么？也许这很简单，但我是软件新手。

如果汽车价格低于 10 并且汽车品牌名称低于 2 个字符，我会尝试获取错误消息。

Answer 1

您的代码看起来不完整，您提出的问题也不是很容易理解。

据我所知，这应该有帮助：

using System;
using System.Collections.Generic;

public class Car
{
    public int Id { get; set; }
    public int BrandId { get; set; }
    public int ColorId { get; set; }
    public decimal DailyPrice { get; set; }
    public string Description { get; set; }
    public int ModelYear { get; set; }
    public string BrandName { get; set; }
}

public class CarManager
{
    private List<Car> _cars = new List<Car>
    {
        new Car { Id = 1, BrandId = 1, ColorId = 13, DailyPrice = 30000, Description = "BMW 5.20", ModelYear = 2023, BrandName = "BMW"},
        new Car { Id = 2, BrandId = 1, ColorId = 13, DailyPrice = 5, Description = "BMW 5.20", ModelYear = 2023, BrandName= "B"},
        new Car { Id = 3, BrandId = 3, ColorId = 10, DailyPrice = 25000, Description = "Mercedes C180", ModelYear = 2023, BrandName="Mercedes"},
        new Car { Id = 4, BrandId = 5, ColorId = 11, DailyPrice = 21000, Description = "Hyundai i20n", ModelYear = 2023, BrandName= "BMW"},
        new Car { Id = 5, BrandId = 3, ColorId = 10, DailyPrice = 40000, Description = "Mercedes A180", ModelYear = 2023, BrandName="Mercedes"},
    };

    public void Add(Car car)
    {
        if (car.DailyPrice > 10 && car.BrandName.Length > 2)
        {
            _cars.Add(car);
        }
        else
        {
            Console.WriteLine("Error: The car must have a daily price greater than 10 and a brand name longer than 2 characters.");
        }
    }
}

class Program
{
    static void Main()
    {
        CarManager carManager = new CarManager();

        Car newCar1 = new Car
        {
            Id = 6,
            BrandId = 2,
            ColorId = 14,
            DailyPrice = 15000,
            Description = "Audi A4",
            ModelYear = 2023,
            BrandName = "Audi"
        };

        Car newCar2 = new Car
        {
            Id = 7,
            BrandId = 4,
            ColorId = 12,
            DailyPrice = 8,
            Description = "Cheap Car",
            ModelYear = 2023,
            BrandName = "CC"
        };

        carManager.Add(newCar1); // This should be added successfully.
        carManager.Add(newCar2); // This should print an error message.
    }
}

说明：

1. 汽车类别：定义汽车的属性。
2. CarManager 类：包含汽车列表和 Add 方法，用于根据特定条件将新汽车添加到列表中。
3. 添加方法：检查汽车每日价格是否大于10，品牌名称长度是否大于2个字符，然后添加到列表中。如果不满足条件，则会打印错误消息。
4. 程序类：演示使用 CarManager 类添加新车，并展示 Add 方法如何处理有效和无效输入。

给定的解决方案确保只有符合指定标准的汽车才会添加到列表中，从而保持汽车集合的完整性。