So I'm studying c# and I've come across the issue where I seem to be getting the error System.Collections.Generic.List`1[Prog2Prov.Program Order] when trying to print out the list and my code currently looks like this. I'm aware that there may be a lot of errors, however, I am still trying to grasp my hands around how c# works. Thanks for all the advice.

 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();
            }

CodePudding user response：

I've come across the issue where I seem to be getting the error System.Collections.Generic.List`1[Prog2Prov.Program Order] when trying to print out the list

There are a few issue's I've found in the above code. First I'll address the actual issue.

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

You're printing the string representation of your List<Order> which is System.Collections.Generic.List1[Prog2Prov.Program Order]. Instead you need to print each Order in that list. As mentioned in my comments above you can do a simple foreach or linq:

Here's the foreach:

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

Here's linq:

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

Another option, if you don't want to do this, you can inherit the List<T> and override the ToString in your new class.

using System.Linq;

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

Then you can use the new list:

 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());

Here's my output from above:

Another issue I seen was:

 town.ToList();

As well as:

 country.ToList();

Both of these are defined as string, you'll still have an issue when printing them out, you need to remove the ToList() on them.

CodePudding user response：

Use a discriminated union via OneOf library.

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

However, polymorphism is much better for this scenario

CodePudding user response：

You can add two objects to the same list. You need to create an object list for that.

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