How to determine number of objects in array

Question

Once again I cannot find a solution myself (I have tried using Array.IndexOf(db, accnum) with a pos > -1 return boolean, but have reverted to this loop after I couldn't make it work). So, I thought using db.Length would leave 'a' at the length of all the non-null elements in the array, however it seems to count the whole array, meaning that when the loop reaches a null element it causes an error. Is there a way to halt the loop count when it runs out of objects in the array?

void withdrawal()
{
    int accnum;
    double withdrawal;

    //get and parse input details
    accnum = int.Parse(tbNameEnt.Text);
    withdrawal = double.Parse(tbBalaEnt.Text);

    //check if account exists within existing objects
    int a = db.Length;
    for (int i = 0; i < a; i++)
    {
        if (db[i].GetAccNo() == accnum)
        {
            pos = i;

            //deduct from balance
            db[pos].SetBalance(db[pos].GetBalance() - withdrawal);

            WithMess(); //success message
            hide_form();
            MakeWith2.Visible = false;
            show_menu();
            break;
        }

        else if ((db[i].GetAccNo() != accnum) && (i == db.Length - 1))
        {
            //account doesn't exist message
            MessageBox.Show("Account does not exist");
        }
    }
}

I have edited your title. Please see, "Should questions include “tags” in their titles?", where the consensus is "no, they should not". — John Saunders
– John Saunders, Commented Feb 27, 2014 at 2:51
Why use an array at all? Why not use a collection, in which case there would be no "empty" items? You can just add and remove and the collection will grow and shrink. — jmcilhinney
– jmcilhinney, Commented Feb 27, 2014 at 2:54

Simon Whitehead · Accepted Answer · 2014-02-27 02:45:08Z

1

If there are null items that pad the array.. break out of the loop when you reach one:

for (int i = 0; i < a; i++) {
   if (db[i] == null)
        break;
   // the rest

Alternatively, use LINQ to filter the null items out:

foreach (var item in db.Where(x => x != null)) {
    // loop here
}

answered Feb 27, 2014 at 2:45

Simon Whitehead

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