How to Add an Item to a Listbox in C# and Winforms

How can I add an item to a ListBox in C# and WinForms?

list.Items.add(new ListBoxItem("name", "value"));

The internal (default) data structure of the ListBox is the ListBoxItem.

Adding Items to a listBox in a Windows Forms Application,

Well, it looks like you're first adding the value from the name TextBox and then the value from the Birth date TextBox. Since birth date is empty here, you'll get an empty string (thus an empty row) on the ListBox.

If you don't want empty values added, you should check for them before the call to the Add method:

if (equal2 == false && !string.IsNullOrEmpty(textBox2.Text)
{
    listBox1.Items.Add(textBox2.Text);
}

However, what you're doing doesn't seem very straight forward. I'd recommend yo rethink the way you check for values and process them.

Adding a value to a listbox item. C#

Yes, ListBox Items are of type object and you can assign any object to them, so build a class like this:

public class ListItem
{
    public string Name {get; set;}
    public int Value {get; set;}

    public override string ToString()
    {
         return Name;
    }
}

Now you can add ListBox Items like this:

listbox.Items.Add(new ListItem { Name = "Test1", Value = 2});

When a ListBox Item is Selected you can get its value like:

var value = ((ListItem)listbox.SelectedItem).Value;

Note that as ListBox Uses its Items .ToString() method to create Texts to show so you have to override it's ToString() method like this:

public override string ToString()
{
    return Name;
}

Otherwise it will show the name of the class instead of your desired value.

Save and load listbox items added by user in c# with windows form app

You need to save the settings

private void AddTeamButton_Click(object sender, EventArgs e)
{
  // add the item to the listbox
  listBox1.Items.Add("Example string);
  // add the item to the ListBoxStuff settings 
  Settings.Default["ListBoxStuff"] = Settings.Default["ListBoxStuff"] + "|" + "Example string";
  Settings.Default.Save();
}

Add item to listbox and select it

The SelectedIndex-property is for single-select-lists. However we can use it on multi-lists also within a double-click-events also because a double-click will implicetly select one single item setting the SelecteItem correctly.

So I used this approach that deletes the list of selected entries and adds only that entry I´m interested in.

this.lbx.Items.Insert(this.lbx.SelectedIndex, this.ofdReferences.FileName);
var idx = this.lbx.SelectedIndex;
this.lbx.SelectedIndices.Clear();
this.lbx.SelectedIndices.Add(idx - 1); 

How to add an item to the top of a ListBox

You can use the ItemCollection.Insert Method

For example

myListbox.Items.Insert(0, myItem);

Add items to a ListBox and bind them to an item in another Listbox

DataBinding would be the way to go. The main component to focus on is BindingSource. You could also investigate DataSets for your underlying data because they would give you some flexibility with filtering. But, if this is a small application, and if you're just learning, the following example might be a good start:

Drag a BindingSource for each of your listboxes onto your form. Then, connect each of the ListBox's DataSource properties to a corresponding BindingSource.

Here is an example code behind that shows how to bind your underlying data to each of the BindingSources which are in turn already bound to the listboxes:

namespace WindowsFormsApplication1
{
    public class Game
    {
        public string Name { get; set; }
        public string Group { get; set; }
    }

    public class Group
    {
        public string Description { get; set; }
    }

    public partial class Form1 : Form
    {
        List<Game> _allGames;

        public Form1()
        {
            InitializeComponent();

            _allGames = new List<Game>
            {
                new Game { Name = "Alpha", Group = "" },
                new Game { Name = "Bravo", Group = "One" },
                new Game { Name = "Charlie" , Group = "One"},
                new Game { Name = "Delta", Group = "Two" }
            };

            bindingSource1.DataSource = _allGames;
            listBox1.DisplayMember = "Name";
            listBox1.ValueMember = "Name";

            var groups = new List<Group>
            {
                new Group { Description = "One" },
                new Group { Description = "Two" },
                new Group { Description = "Three" }
            };

            bindingSource2.DataSource = groups;
            listBox2.DisplayMember = "Description";
            listBox2.ValueMember = "Description";
        }

        private void listBox2_SelectedIndexChanged(object sender, EventArgs e)
        {
            var group = listBox2.SelectedValue.ToString();
            bindingSource3.DataSource = _allGames.Where(x => x.Group == group);
            listBox3.DisplayMember = "Name";
        }
    }
}

All this code is doing is binding data to the BindingSource and telling each ListBox which property of the underlying data to display. This example ignores the mechanism that assign each item from listBox1 to the group in listBox2 because I assume you know how to do that or can figure that out.

The event handler for when listBox2 changes just gets which selection was made and creates a list of items from listBox1 that match that item, and then displays those items in listBox3.

Add and delete text to/from ListBox hosted in WinForm using C#

This code makes no sense. You are adding one single item to a list, then convert it to an array (still containg one item) and finally loop through this array, which of course adds one item to the previously cleared listbox. Therefore your listbox will always contain one single item. Why not simply add the item directly?

private void Add_Click(object sender, EventArgs e)
{
    List.Items.Add(textBox1.Text);
}

private void Delete_Click(object sender, EventArgs e)
{
    List.Items.Clear();
}

Also clear the listbox in Delete_Click instead of Add_Click.

---

If you prefer to keep the items in a separate collection, use a List<string>, and assign it to the DataSource property of the listbox.

Whenever you want the listbox to be updated, assign it null, then re-assign the list.

private List<string> ls = new List<string>();

private void Add_Click(object sender, EventArgs e)
{
    string add = textBox1.Text;

    // Avoid adding same item twice
    if (!ls.Contains(add)) {
        ls.Add(add);
        RefreshListBox();
    }
}

private void Delete_Click(object sender, EventArgs e)
{
    // Delete the selected items.
    // Delete in reverse order, otherwise the indices of not yet deleted items will change
    // and not reflect the indices returned by SelectedIndices collection anymore.
    for (int i = List.SelectedIndices.Count - 1; i >= 0; i--) { 
        ls.RemoveAt(List.SelectedIndices[i]);
    }
    RefreshListBox();
}

private void RefreshListBox()
{
    List.DataSource = null;
    List.DataSource = ls;
}

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