CODEWITHSUNDEEP
c#listcsv
Guil75
Guil75

Reputation: 165

Adding data from a csv file to a List using a loop

I am new to developing and this is my first question, so please excuse any misunderstanding in my explanation.

I am trying to import the data from a csv file into a list of objects I defined. My file has 2 columns and 5 rows: 1 for the date and 1 for the volume of products sold that day. My application reads the file, store the data in 2 lists (1 for the date listDate, 1 for the volume of sale listVolume) then combines both data into a new object mySale and adds the object to the final list Car. It works fine as long as I add mySale to Car line by line (OPTION 1 in the code below) but when trying to use a loop (for statement), I always end up with my final list being populated with the last line of the file (OPTION 2 in the code below). During debug, I can see the properties date an volume are correct in mySale before adding it to Car but once the loop is finished, it seems the result has changed :-s I have the following code:

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace dataManip
{
    class Program
    {

        static void Main(string[] args)
        {

            var reader = new StreamReader(File.OpenRead(@"C:\sales.csv"));
            List<DateTime> listDate = new List<DateTime>();
            List<int> listVolume = new List<int>();
            List<mySales> Car = new List<mySales>();

            while (!reader.EndOfStream)
            {
                var line = reader.ReadLine();
                var values = line.Split(',');

                listDate.Add(Convert.ToDateTime(values[0]));
                listVolume.Add(Convert.ToInt32(values[1]));
            }

            mySales mySale = new mySales();

            //OPTION 1
            mySale.date = listDate[3];
            mySale.volume = listVolume[3];

            Car.Add(mySale);


            //OPTION 2
            for (int i = 0; i < listDate.Count(); i++)
            {
                mySale.date = listDate[i];
                mySale.volume = listVolume[i];

                Car.Add(mySale);
            }

                foreach (int p in listVolume)
                Console.WriteLine(p);
                Console.WriteLine("\n"+Car[0].volume);

                Console.ReadLine();
    }

    }

    class mySales
    {
        public DateTime date { get; set; }
        public int volume { get; set; }
    }
}

Upvotes: 1

Views: 154

Answers (1)

Jashaszun
Jashaszun

Reputation: 9270

mySales is a class, which is a reference type. In option 2, you are doing the following:

  1. You create mySale, which now is a reference to a specific instance of mySales.
  2. In the for loop, you modify mySale (which is still a reference to that exact same instance), and then add this same instance to the end of the list.

So at the end, when you've added mySale multiple times, you have a list with multiple references to the same instance.

What you probably want to do is define and instantiate mySale inside of the for loop, not outside.

Upvotes: 2

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