Question

I am trying to move items from one list box to another if they are multiple but I am able to move only few, means less than the count. I am not able to implement via for each and for loop as well.

if (AdvLst.SelectedIndex > -1)
        {
            for (int i = 0; i <= AdvLst.Items.Count - 1; i++)
            {
                if (AdvLst.Items[i].Selected)
                {
                    string _value = AdvLst.SelectedItem.Value;
                    string _text = AdvLst.SelectedItem.Text;
                    ListItem item = new ListItem();
                    item.Text = _text;
                    item.Value = _value;
                    SelectedMortLst.Items.Add(AdvLst.Items[i]);
                    AdvLst.Items.Remove(AdvLst.Items[i]);
                }
            }

}
and via foreach loop:

                foreach (ListItem li in AdvLst.Items)
            {
                if (li.Selected == true)
                {
                    SelectedMortLst.Items.Add(AdvLst.SelectedItem);
                    AdvLst.Items.Remove(AdvLst.SelectedItem);
                }

            }

Answer 1

Solution 1

var selectedItems = AdvLst.Items.Cast<ListItem>().Where(m => m.Selected).ToArray();
SelectedMortLst.Items.AddRange(selectedItems);

//there's no removeRange, so...
foreach(var item in selectedItems)
    AdvLst.Items.Remove(item);

Solution 2 (almost the same)

var selectedItems = AdvLst.Items.Cast<ListItem>().Where(m => m.Selected).ToArray();
foreach(var item in selectedItems) {
   SelectedMortLst.Add(item);
   AdvLst.Items.Remove(item);
}

Solution 3, for loop code corrected

for (int i = 0; i <= AdvLst.Items.Count - 1; i++)
    {
       if (AdvLst.Items[i].Selected)
           {
              string _value = AdvLst.SelectedItem.Value;
              string _text = AdvLst.SelectedItem.Text;
              ListItem item = new ListItem();
              item.Text = _text;
              item.Value = _value;
              SelectedMortLst.Items.Add(AdvLst.Items[i]);
              AdvLst.Items.Remove(AdvLst.Items[i]);
              i--;
            }
      }

cause if you remove an item in the for loop, the count of the collection changes, and the item which is at i+1 place when you remove item has now index i. With i--, your for loop is adapted to that change