How do you remove an item from a listbox in c# invalidoperationexception was unhandled collection was modified

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C#

protected void MoveOne()
        {
            int intNumberOfItems = strAvailableItems.Length;
            if (lsbAvailableList.SelectedItems != null)
            {
                foreach (var item in lsbAvailableList.SelectedItems)
                {

                    //if (lsbAvailableList.SelectedIndex < intNumberOfItems)
                    //{
                    int intLsbAvailableListIndex = lsbAvailableList.SelectedIndex; //get the index
                    lsbSelectedList.Items.Add(item);
                    lsbAvailableList.Items.RemoveAt(intLsbAvailableListIndex);
                    //lsbAvailableList.Items.Remove(lsbAvailableList.SelectedItems[intLsbAvailableListIndex]);
                    string strIndex = intLsbAvailableListIndex.ToString();
                    //int intLsbIndex = lsbAvailableList.Items.Add(item);
                    MessageBox.Show(strIndex);
                    //}
                 }
            }//
         }
        //-----------------------

Posted 10-Feb-14 9:20am

micromaestro

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3 solutions

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Ravi Bhavnani · Answer 1 · 2014-02-10T09:58:00

Here's an overly simplified way of how to safely remove the currently selected items in a list view, without the use of .Tags.

C#

List<listviewitem> itemsToBeRemoved = new List<listviewitem>();
foreach (ListViewItem item in theListView.SelectedItems) {
    itemsToBeRemoved.Add (item);
}
foreach (ListViewItem lvi in itemsToBeRemoved) {
    theListView.Remove (lvi);
}

/ravi

Ravi Bhavnani · Answer 2 · 2014-02-10T09:24:00

Solution 1

You can't remove items from lsbSelectedList.Items while simultaneously querying lsbAvailableList.SelectedItems. I suggest you tag each ListView item (see the .Tag property) and use the tagged values to identify the ones you want to remove.

/ravi

Posted 10-Feb-14 9:24am

Ravi Bhavnani

Comments

Ranjan.D 10-Feb-14 15:28pm

Just by using for loop instead of using foreach must work I believe.

Ravi Bhavnani 10-Feb-14 15:37pm

No, it won't. You can't modify a collection you're traversing.

/ravi

Ranjan.D 10-Feb-14 15:52pm

Yes Ravi. I knew it wasn't with foreach but hopefully there's a way with for loop like the below example. Or use Linq approaches.

var data=new List<string>(){"One","Two","Three"};
for(int i=data.Count - 1; i > -1; i--)
{
if(data[i]=="One")
{
data.RemoveAt(i);
}
}

http://stackoverflow.com/questions/7340757/c-sharp-list-removing-items-while-looping-iterating

BillWoodruff · Answer 3 · 2014-02-10T18:13:00

You can achieve this with 'foreach:

C#

ListBox.SelectedObjectCollection selListItems = listBox1.SelectedItems;

foreach (var itm in selListItems.OfType<string>().ToList())
{
    listBox1.Items.Remove(itm);
}

By converting the ListBox SelectedItems from ListBoxObjectCollection to List<string>, you can iterate and remove without the collectio modification error.

You could also use

C#

selListItems.OfType<object>().ToList()

in the 'foreach loop.

How do you remove an item from a listbox in c# invalidoperationexception was unhandled collection was modified

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How do you remove an item from a listbox in c# invalidoperationexception was unhandled collection was modified

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