autocalculate total value of items in listview when removing item using c#

Question

I\'m using a listview as a shopping cart. I need to know how to recalculate the total value of the cart when I remove an item.

Here is my code for adding to listview;

Answer 1

You can't change the same list in foreach.

foreach (ListViewItem item in lvCart.Items)
{
    if (lvCart.Items[0].Selected)
    {
        lvCart.Items.Remove(lvCart.SelectedItems[0]);
        total += Convert.ToInt32(item.SubItems[1].Text);
    }
}

The solution is create duplicate list and change it:

var newList = lvCart;

foreach (ListViewItem item in lvCart.Items)
{
    if (lvCart.Items[0].Selected)
    {
        newList.Items.Remove(lvCart.SelectedItems[0]);
        total += Convert.ToInt32(item.SubItems[1].Text);
    }
}

Answer 2

Something like this

On the form level declare

private int _listTotal;

Adding - I think here you have some problems because you should add to total when you add the item

private void btnACart_Click(object sender, EventArgs e)
{
    int value = 0;

    for (int i = 0; i < lvCart.Items.Count; i++)
    {
        value += int.Parse(lvCart.Items[i].SubItems[1].Text);
    }
    // how about lvCart.Items.Add(<myVal>)...???
    _listTotal += value; // and here add myVal
    rtbTcost.Text = _listTotal.ToString();
}

Then when removing - you don't want to use any "for-loops" on mutating collection. But "while" works perfectly on mutations

private void btnRemoveItem_Click(object sender, EventArgs e)
{
    int totalRemoved = 0;
    while (lvCart.SelectedItems.Count > 0)
    {
        totalRemoved += Convert.ToInt32(lvCart.SelectedItems[0].SubItems[1].Text);
        lvCart.Items.Remove(lvCart.SelectedItems[0]);
    } 
    _listTotal -= totalRemoved;
    rtbTcost.Text = _listTotal.ToString

}

Not tested but should work

Answer 3

private void btnRemoveItem_Click(object sender, EventArgs e)
{
    int total = 0;
    foreach (ListViewItem item in lvCart.Items)
    {
       if (lvCart.Items[0].Selected)
        {
            total+=(int)lvCart.SelectedItems[0].SubItems[1].Text;//Add to total while romving
           lvCart.Items.Remove(lvCart.SelectedItems[0]);
           //total += Convert.ToInt32(item.SubItems[1].Text);
        }
    }

      rtbTcost.Text = total.ToString();
   }