Listbox behavior

Question

I have a CheckedListBox and a ListBox. When someone selects an item in the CheckedListBox, it shows up in the ListBox Item List. I also want to be able to remove items from the ListBox which will cause the item in the CheckedListBox to be unselected. I have been successful in adding items to the ListBox from the CheckedListBox when selected. I am having trouble removing items from the Listbox and unselecting them from the CheckedListBox. The strange thing is that it works when I remove the item from the ListBox. When I try to unselect the item from the CheckedListBox, it causes the ListBox to leave ghost items in the ListBox. I am including the code I use for removing the item from the ListBox. When I comment out the code to uncheck the CheckedListBox, it works correctly, When I uncomment this code, it does not work correctly. Help!!!

            string PlayerRemoved;
            int itemcount;
            int itemindex;
            int nbrply;

            itemcount = SelectedPlayersListBox.Items.Count;
            itemindex = SelectedPlayersListBox.SelectedIndex;

            // Get the player selected.
            PlayerRemoved = SelectedPlayersListBox.Text;
            // Make sure that the player is not null.
            if (PlayerRemoved != null)
            {
                // Remove the Player from the list.
                SelectedPlayersListBox.Items.Remove(PlayerRemoved);
                // Get the index of the Player removed from the Available List.
				

//These are the two lines of code that cause the ListBox to behave incorrectly.
                //itemindex = AvailablePlayerListBox.Items.IndexOf(PlayerRemoved);
                // Uncheck the box next to the Players name.
                //AvailablePlayerListBox.SetItemChecked(itemindex, false);
            }


            // Reduce the number of players by one.
            nbrply = Int32.Parse(NbrofPlayers.Text);
            nbrply -= 1;
            NbrofPlayers.Text = nbrply.ToString();
            NbrofPlayers.Refresh();

            SelectedPlayersListBox.Refresh();

Answer 1

Hi @John Pike , Welcome to Microsoft Q&A.

Just use the correct logic in the checklistbox: add when checked, remove when unchecked.

button1, button2 are remove and removeAll respectively.

private void checkedListBox1_ItemCheck(object sender, ItemCheckEventArgs e)
{
    var selectItem = checkedListBox1.SelectedItem;
    bool isChecked = checkedListBox1.GetItemChecked(checkedListBox1.SelectedIndex);
    if (!isChecked)
    {
        listBox1.Items.Add(selectItem);
    }
    else
    {
        listBox1.Items.Remove(selectItem);
    }
    //Get the correct amount at now
    BeginInvoke(new Action(() =>
    {
        textBox1.Text = checkedListBox1.CheckedItems.Count.ToString();
    }));
}

private void button1_Click(object sender, System.EventArgs e)
{
    if (listBox1.SelectedItem == null)
        return;
    var item = listBox1.SelectedItem;
    int index = checkedListBox1.Items.IndexOf(item);
    checkedListBox1.SelectedItem = item;
    checkedListBox1.SetItemChecked(index, false);
    textBox1.Text = checkedListBox1.CheckedItems.Count.ToString();
}

private void button2_Click(object sender, System.EventArgs e)
{
    for (int i = checkedListBox1.Items.Count - 1; i >= 0; i--)
    {
        checkedListBox1.SetItemChecked(i, false);
    }
    listBox1.Items.Clear();
    textBox1.Text = checkedListBox1.CheckedItems.Count.ToString();
}

Best Regards,

Jiale

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Answer 2

If you are still looking for a solution these extension methods can help but have not included how to use them but can if still need a solution.

public static class CheckedListBoxExtensions
{
    /// <summary>
    /// Get checked items as <see cref="T"/>
    /// </summary>
    /// <typeparam name="T">Model</typeparam>
    /// <param name="sender">CheckedListBox</param>
    /// <returns>List if one or more items are checked</returns>
    public static List<T> CheckedList<T>(this CheckedListBox sender)
        => sender.Items.Cast<T>()
            .Where((item, index) => sender.GetItemChecked(index))
            .Select(item => item)
            .ToList();

    /// <summary>
    /// Get all <typeparamref name="T"/> items
    /// </summary>
    /// <param name="sender">CheckedListBox</param>
    /// <returns></returns>
    public static List<CheckedData<T>> IndexList<T>(this CheckedListBox sender) =>
    (
        from item in sender.Items.Cast<T>()
            .Select(
                (model, index) =>
                    new CheckedData<T>
                    {
                        Index = index,
                        Model = model
                    }
            )
            .Where((x) 
                => sender.GetItemChecked(x.Index))
        select item
    ).ToList();

    /// <summary>
    /// Uncheck all items
    /// </summary>
    /// <param name="sender">CheckedListBox</param>
    public static void UnCheckAll(this CheckedListBox sender)
    {
        foreach (int index in sender.CheckedIndices)
        {
            sender.SetItemCheckState(index, CheckState.Unchecked);
        }
    }

    /// <summary>
    /// Find item, set check state for <see cref="T"/>
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="sender">CheckedListBox</param>
    /// <param name="text">text to locate case insensitive</param>
    /// <param name="checked">set check state to</param>
    public static void SetChecked<T>(this CheckedListBox sender, string text, bool @checked)
    {
        var result = sender.Items.Cast<T>().Select((item, index) => 
            new
            {
                Item = item as IBase, 
                Index = index
            })
            .FirstOrDefault(@this => 
                string.Equals(@this.Item!.Name, text, StringComparison.CurrentCultureIgnoreCase));

        if (result != null)
        {
            sender.SetItemChecked(result.Index, @checked);
        }
    }
}