如何將2個不同的類添加到同一個串列中？

所以我正在學習 c# 并且我遇到了一個問題，當我嘗試列印串列時我似乎收到錯誤 System.Collections.Generic.List`1[Prog2Prov.Program Order] 并且我的代碼目前看起來像這樣。我知道可能有很多錯誤，但是，我仍然試圖掌握 c# 的作業原理。感謝所有的建議。

 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();

                string name, location, date;
                int number;

                if (parcel == "N")
                {
                    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 == "S")
                {
                    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();

                    orders.Add(new NormalOrder(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)");
                    string shipping = Console.ReadLine();
                    foreach(var order in orders)
                    if (shipping == "t")
                    {
                        Console.WriteLine(order);

                    }
                    else if (shipping == "C")
                    {
                        Console.WriteLine(order);
                    }
                    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()
            {
                return "Order name: "   orderName  "\nOrder number: "   orderNumber   "\nOrder date: "   orderDate   "\nOrder location:"   town.ToList();
            }
        }

        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()
            {
                return "Order name: "   orderName   "\nOrder number: "   orderNumber   "\nOrder date: "   orderDate   "\nOrder location:"   country.ToList();
            }

uj5u.com熱心網友回復：

我遇到了在嘗試列印串列時出現錯誤 System.Collections.Generic.List`1[Prog2Prov.Program Order] 的問題

我在上面的代碼中發現了一些問題。首先，我將解決實際問題。

 if (shipping == "t")
 {
    Console.WriteLine(orders);
 }

您正在列印List<Order>which is的字串表示形式System.Collections.Generic.List1[Prog2Prov.Program Order]。相反，您需要列印Order該串列中的每個。正如我在上面的評論中提到的，你可以做一個簡單的foreach或linq：

這是foreach：

 foreach(var o in orders) 
    Console.WriteLine(o);

這是linq：

 Console.WriteLine(string.Join('\n', orders.Select(o => o.ToString())));     

另一種選擇，如果你不想這樣做，你可以繼承List<T>，并override在ToString您的新類。

using System.Linq;

public class OrderList : List<Order>
{
   public override string ToString() => string.Join("\n", this.Select(o => o.ToString()));

然后您可以使用新串列：

 OrderList ol = new OrderList();
 ol.Add(new NormalOrder("order 1", 1, DateTime.Now.ToString(), "Nowhere Town"));
 ol.Add(new SpecialOrder("special order 2", 2, DateTime.Now.ToString(), "Nowhere Town 2"));
 MessageBox.Show(ol.ToString());

這是我上面的輸出：

我看到的另一個問題是：

 town.ToList();

也：

 country.ToList();

這兩個都定義為string，列印它們時仍然會遇到問題，您需要洗掉ToList()它們上的 。

uj5u.com熱心網友回復：

通過OneOf庫使用可區分聯合。

var myList = new List<OneOf<SpecialOrder, NormalOrder>>()
{
    new NormalOrder(...), new SpecialOrder(...)
};
myList[0].Switch(
    special => Console.WriteLine("Special"),
    normal => Console.WriteLine("Normal"),
);

但是，多型性對于這種情況要好得多

uj5u.com熱心網友回復：

您可以將兩個物件添加到同一個串列中。您需要為此創建一個物件串列。

List<object> list = new List<object>();
list.Add(objType1);
list.Add(objType2);

標籤：C＃

上一篇：從串列中獲取不同的字串，然后創建一個新物件并將其添加到同一個串列中

下一篇：預備知識-python核心用法常用資料分析庫（下）