Items in a ListBox appear as a class name

Question

The problem is this: I linked ListBoxto a list of elements of some custom class ( List<Person> persons = new List<Person>()) using a property DataSource. Of course, ValueMemberand DisplayMembertwo appointed by the properties of this class. When I first upload the data, everything looks fine. However, when I click on an element (i.e. the 7th position, counting from 1), and then rebuild the list AND the number of elements is less than MANY, as a result I do not see the corresponding texts in the list. Instead, each element is displayed as a class name preceded by a namespace.

In other words, instead of a list:

• John doe
• Jane doe
• Someone else

I see it:

• MyNamespace.Person
• MyNamespace.Person
• MyNamespace.Person

, SelectedIndex. ( ), .

ValueMember DisplayMember, null DataSource , -1 SelectedIndex , .

[]

. :

1. :

public class Person
{
    private int id;
    private string name;

    public Person(int m_id, string m_name)
    {
        id = m_id;
        name = m_name;
    }

    public int Id
    {
        get
        {
            return id;
        }
    }

    public string Name
    {
        get
        {
            return name;
        }
    }
}`

2. :

List<Person> persons = new List<Person>();

3. , 1, :

listBox1.DataSource = null;    // this is optional. Commenting this line out doesn't help
persons.Add(new Person(1, "John Doe"));
persons.Add(new Person(2, "Jane Doe"));
persons.Add(new Person(3, "Somebody Else"));
listBox1.ValueMember = "Id";
listBox1.DisplayMember = "Name";
listBox1.DataSource = persons;

4. , buton2, :

listBox1.DataSource = null;    // this is optional. Commenting this line out doesn't help
persons.Add(new Person(1, "Person One"));
persons.Add(new Person(2, "Person Two"));
listBox1.ValueMember = "Id";
listBox1.DisplayMember = "Name";
listBox1.DataSource = persons;

1, , . ( "Somebode Else" ), clisk button2, 2 : "MyNamespace.Person".

[ 2 - ]

using System;
using System.Collections.Generic;
using System.Windows.Forms;

namespace MyNamespace
{
    public partial class Form1 : Form
    {
        private List<Person> persons = new List<Person>();
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            persons.Clear();
            persons.Add(new Person(1, "John Doe"));
            persons.Add(new Person(2, "Jane Doe"));
            persons.Add(new Person(1, "Somebody Else"));
            listBox1.DataSource = null;
            listBox1.ValueMember = "Id";
            listBox1.DisplayMember = "Name";
            listBox1.DataSource = persons;
        }

        private void button2_Click(object sender, EventArgs e)
        {
            persons.Clear();
            persons.Add(new Person(1, "Person One"));
            persons.Add(new Person(2, "Person Two"));
            listBox1.DataSource = null;
            listBox1.ValueMember = "Id";
            listBox1.DisplayMember = "Name";
            listBox1.DataSource = persons;
        }
    }

    class Person
    {
        private int id;
        private string name;

        public Person(int m_id, string m_name)
        {
            id = m_id;
            name = m_name;
        }

        public int Id
        {
            get
            {
                return id;
            }
        }

        public string Name
        {
            get
            {
                return name;
            }
        }

        public string ToString()
        {
            return id + ". " + name;
        }
    }
}

:

• 1
• ( "Somebody Else" )
• 2

"John Doe" "Jane Doe" , . , "", . , .

Answer 1

Person ToString:

public class Person
{
    private int id;
    private string name;

    public Person(int m_id, string m_name)
    {
        id = m_id;
        name = m_name;
    }

    public int Id
    {
        get
        {
            return id;
        }
    }

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

, listbox List<Person>, ToString . - Person, (Person)listBox1.SelectedItem.

, null, DisplayMemeber. , , .

listBox1.DataSource = null;    // this is optional. Commenting this line out doesn't help
persons.Add(new Person(1, "John Doe"));
persons.Add(new Person(2, "Jane Doe"));
persons.Add(new Person(3, "Somebody Else"));
listBox1.DataSource = persons;
listBox1.DisplayMember = "Name";

Answer 2

ValueMember "" DisplayMember " . ? , , ListBox" ClearSelected()" - . , , . , . , .