C#如何将两个不同类的实例添加到同一个List集合并正常打印内容

打印异常核心原因及代码问题整理 #

• ToString方法中错误调用ToList()：字符串类型的town/country被转为List<char>，拼接输出时会打印集合类型名而非实际地址内容
• 特殊订单分支逻辑错误：选择S（特殊订单）时仍然实例化NormalOrder，SpecialOrder类完全未被使用
• 执行逻辑顺序错误：收件地址类型判断写在foreach循环内部，每遍历一个订单就重复判断一次用户输入，输入错误时会重复打印N次错误提示（N为订单总量）
• 大小写匹配逻辑缺失：提示输入T=Town，代码判断条件为小写t，用户输入大写T会被判定为输入错误
• 程序无退出路径：close变量始终为true，循环无法正常终止
• 缺少类型筛选逻辑：选择查看城镇/国家地址时，未过滤对应订单类型，所有订单都会被输出

修复后的代码示例 #

List<Order> orders = new List<Order>();
bool close = true;
while (close)
{
    Console.WriteLine("What type of order is this?(N=Normal/S=Special/#=End)");
    string parcel = Console.ReadLine().Trim();

    string name, location, date;
    int number;

    if (parcel.Equals("N", StringComparison.OrdinalIgnoreCase))
    {
        Console.Write("Enter the name of your order: ");
        name = Console.ReadLine();
        Console.Write("Enter your order number: ");
        number = Convert.ToInt32(Console.ReadLine());
        Console.Write("Enter your order date: ");
        date = Console.ReadLine();
        Console.Write("Enter your town: ");
        location = Console.ReadLine();
        orders.Add(new NormalOrder(name, number, date, location));
    }
    else if (parcel.Equals("S", StringComparison.OrdinalIgnoreCase))
    {
        Console.Write("Enter the name of your order: ");
        name = Console.ReadLine();
        Console.Write("Enter your order number: ");
        number = Convert.ToInt32(Console.ReadLine());
        Console.Write("Enter your order date: ");
        date = Console.ReadLine();
        Console.Write("Enter your country: ");
        location = Console.ReadLine();
        // 修正为实例化SpecialOrder
        orders.Add(new SpecialOrder(name, number, date, location));
    }
    else if (parcel == "#")
    {
        Console.WriteLine("Do you want to see which countries or town your sent your parcel to?(C=Country/T=Town/E=Exit)");
        string shipping = Console.ReadLine().Trim();
        // 先判断输入类型再遍历订单
        if (shipping.Equals("T", StringComparison.OrdinalIgnoreCase))
        {
            Console.WriteLine("=== 城镇地址订单列表 ===");
            foreach (var order in orders.OfType<NormalOrder>())
            {
                Console.WriteLine(order);
                Console.WriteLine("-------------------");
            }
        }
        else if (shipping.Equals("C", StringComparison.OrdinalIgnoreCase))
        {
            Console.WriteLine("=== 国家地址订单列表 ===");
            foreach (var order in orders.OfType<SpecialOrder>())
            {
                Console.WriteLine(order);
                Console.WriteLine("-------------------");
            }
        }
        else if (shipping.Equals("E", StringComparison.OrdinalIgnoreCase))
        {
            // 退出循环
            close = false;
            Console.WriteLine("程序即将退出");
        }
        else
        {
            Console.WriteLine("Incorrect input, try again!");
        }
    }
    else
    {
        Console.WriteLine("Incorrect input, try again!");
    }
}

class Order
{
    protected string orderName { get; set; }
    protected int orderNumber { get; set; }
    protected string orderDate { get; set; }
}       

class NormalOrder : Order
{
    private string town { get; set; }
    public NormalOrder(string orderName, int orderNumber, string orderDate, string town)
    {
        this.orderName = orderName;
        this.orderNumber = orderNumber;
        this.orderDate = orderDate;
        this.town = town;
    }
    public override string ToString()
    {
        // 删掉多余的ToList()调用
        return $"Order name: {orderName}\nOrder number: {orderNumber}\nOrder date: {orderDate}\nOrder location: {town}";
    }
}

class SpecialOrder : Order
{
    private string country;
    public SpecialOrder(string orderName, int orderNumber, string orderDate, string country)
    {
        this.orderName = orderName;
        this.orderNumber = orderNumber;
        this.orderDate = orderDate;
        this.country = country;
    }
    public override string ToString()
    {
        // 删掉多余的ToList()调用
        return $"Order name: {orderName}\nOrder number: {orderNumber}\nOrder date: {orderDate}\nOrder location: {country}";
    }
}

额外优化建议 #

• 订单号输入可增加异常捕获，避免用户输入非数字内容导致程序崩溃
• 订单日期可改用DateTime类型存储，方便后续做时间维度的筛选
• 可给Order基类增加抽象的GetLocation()方法，无需依赖OfType做类型筛选

内容的提问来源于stack exchange，提问作者Zeorth