C#•2y ago

✅ How to add data to a list that is outside of Main()?

using System.Collections.Generic;
internal class Program
{
    public static void insertData(string animal, int amount)
    {
        var list = new List<KeyValuePair<string, int>>();
        list.Add(new KeyValuePair<string, int>(animal, amount));
    }
    private static void Main(string[] args)
    {
        insertData("Dog", 4);
        insertData("Cat", 12);

        foreach(var element in list)
        {
            Console.WriteLine(element);
        }
    }
}

using System.Collections.Generic;
internal class Program
{
    public static void insertData(string animal, int amount)
    {
        var list = new List<KeyValuePair<string, int>>();
        list.Add(new KeyValuePair<string, int>(animal, amount));
    }
    private static void Main(string[] args)
    {
        insertData("Dog", 4);
        insertData("Cat", 12);

        foreach(var element in list)
        {
            Console.WriteLine(element);
        }
    }
}

I know there are some errors but I can't figure out how to solve this. Also when calling the insertData the list will be resetted every new call?

13 Replies

VydrOz•2y ago

yes cause you declare it in the method insertData, So list is not accessible in main you must instantiate your list variable externally OR pass it directly into the method and return it / using reference

MODiX•2y ago

RubyNova#0404

if you're unsure of by ref. vs. by val. look at this gif until it makes sense: https://media.giphy.com/media/xUPGcLrX5NQgooYcG4/giphy.gif

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<@!358653201513447465> from #chat (click here)

React with ❌ to remove this embed.

DiMiaNOP•2y ago

geez I dont even know what the word instantiate means. I dont even know where to begin

VydrOz•2y ago

declaration : List<KeyValuePair<string, int>> list; instantiation : list = new List<KeyValuePair<string, int>>();

Declaring a variable means to introduce a new variable to the program. You define its type and its name. Instantiate - Instantiating a class means to create a new instance of the class.

VydrOz•2y ago

src https://stackoverflow.com/questions/32290879/meanings-of-declaring-instantiating-initializing-and-assigning-an-object

Stack Overflow

Meanings of declaring, instantiating, initializing and assigning an...

Technically what are the meanings and differences of the terms declaring, instantiating, initializing and assigning an object in C#? I think I know the meaning of assigning but I have no formal

DiMiaNOP•2y ago

thanks, appreciated. now I follow 🙂

VydrOz•2y ago

DiMiaNOP•2y ago

using System.Collections.Generic;
internal class Program
{
    private static List<Animals> animalList = new List<Animals>();
    public class Animals
    {
        public string Name { get; set; }
        public int Amount { get; set; }

        public Animals(string Name, int Amount)
        {
            this.Name = Name;
            this.Amount = Amount;
        }
    }
    public static void insertData(string animal, int amount)
    { 
        animalList.Add(new Animals(animal, amount));
    }
    private static void Main(string[] args)
    {
        insertData("Dog", 4);
        insertData("Cat", 12);

        foreach (Animals animals in animalList)
        {
            Console.WriteLine(animals.Name);
        }
    }
}

using System.Collections.Generic;
internal class Program
{
    private static List<Animals> animalList = new List<Animals>();
    public class Animals
    {
        public string Name { get; set; }
        public int Amount { get; set; }

        public Animals(string Name, int Amount)
        {
            this.Name = Name;
            this.Amount = Amount;
        }
    }
    public static void insertData(string animal, int amount)
    { 
        animalList.Add(new Animals(animal, amount));
    }
    private static void Main(string[] args)
    {
        insertData("Dog", 4);
        insertData("Cat", 12);

        foreach (Animals animals in animalList)
        {
            Console.WriteLine(animals.Name);
        }
    }
}

Am I even doing something right here or?

VydrOz•2y ago

you need to add using System; to call Console.WriteLine() otherwise the code seems correct i guess you are learning to code, but if you put everything in the Program.cs, it is a good practice to put the main method on top

DiMiaNOP•2y ago

yeah Im a beginner. Ive worked a little bit with python and php before

VydrOz•2y ago

and separate the class Animal (without "s") in an other file

DiMiaNOP•2y ago

alright, thanks alot man I will close this if there is nothing more to add

VydrOz•2y ago

yep

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Programming

✅ How to add data to a list that is outside of Main()?