Issues adding items and expanding the collections list of checkedlistbox on a windows form in c#

Question

Hi, This may seem like a dumb question. I have a textbox that can be used to add items to a checkedlistbox at runtime on a windows form. I'm using c#. It works perfectly fine at runtime. The item gets added and stuff, when the form is open. But, when I close and open the form again, I don't see the added item in the checkedlistbox list. Note, I don't use a datasource and don't want to. I wouldn't want to hardcode anything and would prefer to use a textbox input on the form as a variable to feed into the collections list. I couldn't figure out a way to expand my checkedlistbox options. Any assistance would be appreciated.

Answer 1

How are you opening the form? Is it something like:

FormName form = new FormName();
form.Show()

The only reason I can think that's happening is that you're instantiating a new form instance every time you show it, instead of reusing the same form.

Answer 2

Have your Form take a ref List<string> values as parameter. Then make this as BindingSource for the CheckedListBox.

Here is the code:

class MyForm : Form {
        List<string> values;
        BindingSource source;

        public MyForm()
        {
            InitializeComponent();
        }

        public MyForm(ref List<string> values):this()
        {
            if (values == null)
                values = new List<string>();

            this.values = values;

            checkedListBox1.DisplayMember = "Value";
            checkedListBox1.ValueMember = "Value";
            source = new BindingSource(this.values, null);
            checkedListBox1.DataSource = source;
        }

        private void AddItemButton_Click(object sender, EventArgs e)
        {
            this.source.Add(textBox1.Text);
            textBox1.Text = string.Empty;
        }
}

Answer 3

private void frmMain_Load(object sender, EventArgs e)
{
  if (!string.IsNullOrEmpty(Properties.Settings.Default.CheckedItems))
  {
    string[] checkedIndicies = Properties.Settings.Default.CheckedItems.Split(new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries);
    for (int i1 = 0; i1 < checkedIndicies.Length; i1++)
    {
      int idx;
      if ((int.TryParse(checkedIndicies[i1], out idx)) && (checkedListBox1.Items.Count >= (idx+1)))
      {
        checkedListBox1.SetItemChecked(idx, true);
      }
    }
  }
}

private void button2_Click(object sender, EventArgs e)
    {
        if (textBox1.Text != "")
        {
            textBox1.MaxLength = 15;
            // Change all text entered to be lowercase.
            textBox1.CharacterCasing = CharacterCasing.Lower;

            if (checkedListBox1.Items.Contains(textBox1.Text) == false)
            {
                checkedListBox1.Items.Add(textBox1.Text, CheckState.Checked);

                textBox1.Text = "";
                MessageBox.Show("Added! Click Move to see List Box");
            }

            else
            {
                MessageBox.Show("Already There!");
                textBox1.Text = "";
            }
        }
    }



private void frmMain_FormClosing(object sender, FormClosingEventArgs e)
{
  string idx = string.Empty;
  for (int i1 = 0; i1 < checkedListBox1.CheckedIndices.Count; i1++)
    idx += (string.IsNullOrEmpty(idx) ? string.Empty : ",") + Convert.ToString(checkedListBox1.CheckedIndices[i1]);
  Properties.Settings.Default.CheckedItems = idx;
  Properties.Settings.Default.Save();
}