Index out of range exception while inserting elements into a list

Question

I keep getting the following error: "Index was out of range. Must be non-negative and less than the size of the collection", while executing the following code:

 try
        {
            string connectionstring = "server=localhost;user id=root;database=itemdb;password=root";
            MySqlConnection conn = new MySqlConnection(connectionstring);
            conn.Open();
            MySqlCommand cmd = new MySqlCommand("SELECT item.item_name,location.city,time.month,SUM(unit_sales) FROM sales_fact,time,item,location WHERE(sales_fact.item_key = item.item_key AND sales_fact.location_key = location.location_key AND sales_fact.time_key = time.time_key) GROUP BY item.item_name", conn);
            MySqlDataReader dr = cmd.ExecuteReader();
            int c = 0;
            List<Cube1> cubelist = new List<Cube1>();
            while (dr.Read())
            {
                //i++;
                cubelist[c].itemname = dr.GetValue(0).ToString();
                cubelist[c].city = dr.GetValue(1).ToString();
                cubelist[c].month = dr.GetValue(2).ToString();
                cubelist[c].totalsales = (int)dr.GetValue(3);
                MessageBox.Show(cubelist[0].totalsales.ToString());
                c++;
            }
            dr.Close();
            MySqlDataAdapter da = new MySqlDataAdapter(connectionstring, conn);
            DataSet dt = new DataSet();
            da.Fill(dt);
            dataGridView1.DataSource = dt;
            conn.Close();
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }

Where I'm going wrong?

You should be doing cubelist.Add().

Rick S
– Rick S

2014-04-27 21:18:38 +00:00
Commented Apr 27, 2014 at 21:18 — Rick S
– Rick S, Commented Apr 27, 2014 at 21:18
Min mod: change //i++; to cubelist.Add(new Cube1());

Ulugbek Umirov
– Ulugbek Umirov

2014-04-27 21:18:41 +00:00
Commented Apr 27, 2014 at 21:18 — Ulugbek Umirov
– Ulugbek Umirov, Commented Apr 27, 2014 at 21:18

Selman Genç · Accepted Answer · 2014-04-27 21:18:00Z

2

Your list is empty, but you are trying to access it's elements.You should use List<T>.Add method first. In your code:

new List<Cube1>(100);

100 only specifies the Capacity, it isn't the size of your list.It is used to allocate an array with specified length to avoid re-allocation every time you add a new item to your list.

cubelist.Add(new Cube());
cubelist[c].itemname = dr.GetValue(0).ToString();
cubelist[c].city = dr.GetValue(1).ToString();
...

answered Apr 27, 2014 at 21:18

Selman Genç

102k15 gold badges126 silver badges193 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Steve Over a year ago

The Poster has changed its code now, but not the title :-)

Selman Genç Over a year ago

@Steve yea you right but still the same exception remains. :) the indexer of List<T> throws exception, in order to get nullreference you should have at least a null item :)

Ant P · Accepted Answer · 2014-04-27 21:49:13Z

You create a new (empty) List<Cube1> and then try to assign to properties of elements that don't exist because the list is empty. Instead of using cubelist[c], you need to be doing var cube = new Cube1() to instantiate a new Cube1, then assigning the values to its properties, then adding that to the list using cubelist.Add(cube).

List<Cube1> cubelist = new List<Cube1>();
while (dr.Read())
{
    // Create a new Cube1 instance
    var cube = new Cube1();

    // Set its properties
    cube.itemname = dr.GetValue(0).ToString();
    cube.city = dr.GetValue(1).ToString();
    cube.month = dr.GetValue(2).ToString();
    cube.totalsales = (int)dr.GetValue(3);

    // Add it to the list
    cubelist.Add(cube);

    MessageBox.Show(cube.totalsales.ToString());
}

You don't need your c variable at all.

Collectives™ on Stack Overflow

Index out of range exception while inserting elements into a list

2 Answers 2

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related