How to loop to add items up to a quantity

Question

I'm trying to make a loop to add 10 items but only add one with the number 10.

List<Contact> listContact;

for (int cuantidade = 0; cuantidade < 10; cuantidade++)
{
    listContact = new List<Contact>(cuantidade)
    {
        new Contact()
        {
            Name =  cuantidade.ToString(),
            Number = cuantidade.ToString(),
        },
    };
}

this.listBoxNames.ItemsSource = listContact;

What am I doing wrong?

Answer 1

Try this:

var contactList= new List<Contact>();

for (int cuantidade = 0; cuantidade < 10; cuantidade++)
{
    contactList.Add(new Contact
    {
        Name =  cuantidade.ToString(),
        Number = cuantidade.ToString(),
    });
}
this.listBoxNames.ItemsSource = contactList;

Answer 2

You need to set the list before the loop. With your current code, at every iteration the list is redefined and resets...

Answer 3

Here is an alternate example pair using Linq

• The first just gets 10
• The second starts at one point (13) and then gets the next 7

I used a number generator just for the example but it could be any source.

using System;
using System.Linq;
using System.Collections.Generic;

public class Program
{
    public static void Main()
    {
        // Generate a sequence of integers from 9 to 50
        IEnumerable<int> quanityNumbers = Enumerable.Range(9, 50);
        
        // just take the first 10:
        List<Contact> contacts = quanityNumbers
            .Take(10)
            .Select(a => new Contact()
            {
                Name = a.ToString(), 
                Number = a.ToString()
            }).ToList();
        Console.WriteLine($"Hello World contacts has {contacts.Count} items");
        foreach (var c in contacts)
        {
            Console.WriteLine($"contacts has Name: {c.Name} with Number: {c.Number}");
        }
        
        //Start at some point and take 7 from there:
        List<Contact> contactsFromTo = quanityNumbers
            .Skip(13)
            .Take(7)
            .Select(a => new Contact()
            {
                Name = a.ToString(), 
                Number = a.ToString()
            }).ToList();

        Console.WriteLine($"Hello World contactsFromTo has {contactsFromTo.Count} items");
        foreach (var c in contactsFromTo)
        {
            Console.WriteLine($"contactsFromTo has Name: {c.Name} with Number: {c.Number}");
        }
    }

    public class Contact
    {
        public string Name { get; set; }
        public string Number { get; set; }
    }
}