将信息从文本框显示为C＃形式的列表框

Question

I have made the following form and I'm having problems displaying the number of members in the number of members listbox, here is a screenshot before pressing the button 'Add Artist'

and here is what happens when I press Add Artist, as you can see it uses the contents of Artist Name instead of Number of Artists

Here is my code for form1:

 public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

    Dictionary<String, Book> music = new Dictionary<String, Book>();

    private void btnAdd_Click(object sender, EventArgs e)
    {
        if ((txtIsbn.Text != "") & (txtArtist.Text != "")) // if text artist name and number of artists is present
        {
            try { music.Add(txtArtist.Text, new Book(txtArtist.Text, txtIsbn.Text)); } //txtArtist
            catch { MessageBox.Show("Already Exist!!"); }
        }
        else MessageBox.Show("Please fill in both Artist Name and Number of Members");

        listBox1.Items.Clear();
        listBox2.Items.Clear();
        listBox3.Items.Clear();
        foreach (var pair in music)
        {
            listBox1.Items.Add(pair.Key);
            //listBox2.Items.Add(pair.Value.Onloan);
            listBox3.Items.Add(pair.Key);
        }
    }

and here is my code for the Artist class (called book because I edited a program I created before):

class Book
{
    private String mem; //mem = number of members
    private string artist;


    public Book(string mem, string artist)
    {
        this.mem = mem;
        this.artist = artist;
    }

    public string MEM
    {
        get { return mem; }
        set { mem = value; }
    }

    public string Artist
    {
        get { return artist; }
        set { artist = value; }
    }

I've realised that it's adding the value of artist name from the 'Key' command : listBox3.Items.Add(pair.Key);

however I don't know what to change it to.. any help is appreciated thanks alot :)

Answer 1

In your

    foreach (var pair in music)
    {
        listBox1.Items.Add(pair.Key);
        //listBox2.Items.Add(pair.Value.Onloan);
        Book b = pair.Value;
        listBox3.Items.Add(b.MEM);
    }

You don't add the contents of the MEM-property to the listbox. But I don't see any place you are setting it, either.

Answer 2

It's hard to tell for sure, but it seems like you want this inside the foreach loop:

listBox3.Items.Add(pair.Value.MEM);

Also, since the mem argument in your constructor is first, you probably want to swap what you are passing in so that it lines up:

new Book(txtIsbn.Text, txtArtist.Text)

This is assuming that txtArtist.Text contains the value you want for Artist , and txtIsbn.Text contains the value you want for MEM .

As a side note, it's worth your time to clean up the names, it will make it a lot easier to find problems later.

Answer 3

Instead of:

foreach (var pair in music)
        {
            listBox1.Items.Add(pair.Key);
            //listBox2.Items.Add(pair.Value.Onloan);
            listBox3.Items.Add(pair.Key);
        }

I think you want:

foreach (var pair in music)
        {
            listBox1.Items.Add(pair.Key);
            //listBox2.Items.Add(pair.Value.Onloan);
            listBox3.Items.Add(pair.Value.MEM );
        }

Answer 4

You have your music dictionary containing book by artist name.
So the key is the name of the book, and the value is the book.
The right way to do it is :

foreach (var pair in music)
{
    var book = pair.Value;
    listBox1.Items.Add(book.Artist);
    listBox3.Items.Add(book.MEM);
}

Answer 5

Instead of catching exceptions, simply check if book already added into dictionary. Also set books as data source for listbox, instead of adding them manually to items:

private void btnAdd_Click(object sender, EventArgs e)
{
    if (txtIsbn.Text == "" || txtArtist.Text == "")
    {
       MessageBox.Show("Please fill in both Artist Name and Number of Members");
       return;
    }

    Book book = new Book(txtArtist.Text, txtIsbn.Text);

    if (music.ContainsKey(book.Artist))
    {
        MessageBox.Show("Already Exist!!");
        return;
    }

    music.Add(book.Artist, book);
    var books = music.Values.ToList();   

    listBox1.DisplayMember = "Artist"; // set it in designer
    listBox1.DataSource = books;
    listBox3.DisplayMember = "MEM"; // set it in designer
    listBox3.DataSource = books;
}