How to refresh DataSource of a ListBox

Question

Form has one Combobox and one ListBox. When the "Add" button is clicked, I want to add the selected item from the ComboBox to the ListBox.

public partial class MyForm:Form {     List<MyData> data = new List<MyData>();     private void ShowData()     {        listBox1.DataSource = data;        listBox1.DisplayMember = "Name";        listBox1.ValueMember = "Id";     }      private void buttonAddData_Click(object sender, EventArgs e)     {        var selection = (MyData)comboBox1.SelectedItem;        data.Add(selection);        ShowData();     } } 

With this example, the selected item is replaced with the new selection inside ListBox. I need to add the item to the list.

What is wrong with my code?

Answer 1

listbox1.DataSource property looks for value changes but by assigning the same list all the time the value won't really change.

You can use a BindingList<T>, instead of your List<T>, to automatically recognize new items added. Your ShowData() method must be called once at startup.

public partial class MyForm:Form {     public MyForm(){         InitializeComponent();         ShowData();     }      BindingList<MyData> data = new BindingList<MyData>();      private void ShowData()     {        listBox1.DataSource = data;        listBox1.DisplayMember = "Name";        listBox1.ValueMember = "Id";     }      private void buttonAddData_Click(object sender, EventArgs e)     {        var selection = (MyData)comboBox1.SelectedItem;        data.Add(selection);     } }