Adding objects in a List

Question

I want to add objects in a List <T> when I select an item from a combobox, named cmbMaxim. The problem is I obtain a list with the same object (last object added). It's seems like new operator won't work and I obtain a reference to the same object. Here is the code:

public partial class Form1 : Form
{
    List<Varianta> lvar = new List<Varianta>();
    int contor = 0;
    public Form1()
    {
        InitializeComponent();
    }


    private void cmbMaxim_SelectedIndexChanged(object sender, EventArgs e)
    {
        int[] vgen = new int[6];
        int vmax = Convert.ToInt32(cmbMaxim.Text);
        for (int i0 = 1; i0 < vmax - 4; i0++)
            for (int i1 = i0 + 1; i1 < vmax - 3; i1++)
                for (int i2 = i1 + 1; i2 < vmax - 2; i2++)
                    for (int i3 = i2 + 1; i3 < vmax - 1; i3++)
                        for (int i4 = i3 + 1; i4 < vmax; i4++)
                            for (int i5 = i4 + 1; i5 < vmax + 1; i5++)
                            {
                                Varianta var = new Varianta();
                                vgen[0] = i0;
                                vgen[1] = i1;
                                vgen[2] = i2;
                                vgen[3] = i3;
                                vgen[4] = i4;
                                vgen[5] = i5;
                                contor++;
                                var.Var = vgen;
                                var.Index = contor;
                                lvar.Add(var);
                            }
    }
}

Class Varianta is:

class Varianta
{
    int[] var = new int[6];
    int index;
    int scor=0;
    int eliminate=0;

    public int Scor
    {
        get 
        { 
            return scor;
        }
        set 
        { 
            scor = value; 
        }
    }

    public int Index
    {
        get 
        { 
            return index; 
        }
        set 
        { 
            index = value; 
        }
    }


    public int [] Var
    {
        get 
        { 
            return var; 
        }
        set 
        { 
            var = value; 
        }
    }
}

What is wrong?

If Var already has an array allocated, why are you overwritting it with something that is shared across all of the loops? Instead why not just var.Var[0] = i0;, etc.? — crashmstr
– crashmstr, Commented Jul 17, 2015 at 19:05
move the declaration of vgen to the innermost loop. All you objects points to the same array. — EZI
– EZI, Commented Jul 17, 2015 at 19:14
As a side note, since you allocate var already in Varianta, I would personally make Var's set to be private (i.e. you can't assign a new array, but you can access and set the values in the array). — crashmstr
– crashmstr, Commented Jul 17, 2015 at 19:21

Xavier Peña · Accepted Answer · 2015-07-17 19:22:40Z

1

Since you are creating int[] vgen out of the loop, every time you do lvar.Add(var) (where var.Var = vgen), you are pointing to the same variable (int[] vgen).

But at the same time, at every loop you are changing the values of int[] vgen (overwriting the previous ones).

The code is not ok at all. As other people pointed out, 6 nested loops will be a nightmare to debug. But that being said, I guess one simple solution is to declare int[] vgen inside the loop and it will work for you.

Edit: as @crashmstr pointed out, another way to make it work is using var.Var[0] = i0 and so on (instead of using vgen[0] = i0). No need to redeclare int[] vgen inside the loop since it is already initialized inside Varianta.

edited Jul 17, 2015 at 19:22

answered Jul 17, 2015 at 19:12

Xavier Peña

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2 Comments

crashmstr Over a year ago

No need to declare vgen at all, each Varianta already allocates an array, so can just set those values directly.

Triscian Talpineanu Over a year ago

The 6 loops was only for generating the array vgen []. It's a way to generate combination of n numbers in series of 6. No other code will be there. I'm sure there is a better way to do this, but I haven't found it.

Alex Netkachov · Accepted Answer · 2015-07-17 19:09:31Z

0

You need to clear list first. Currently the event adds the items one after another.

    private void cmbMaxim_SelectedIndexChanged(object sender, EventArgs e)
    {
        lvar.Clear();
        int[] vgen = new int[6];
        ...

answered Jul 17, 2015 at 19:09

Alex Netkachov

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