How do I update item quantity in shopping basket when an item is added in to the listbox in C#
<p>I'm currently working on a shopping basket application in C# at the moment.</p>

<p>Is there a way that when I press the add button it can update the item quantity each time that an item is added to the basket?</p>

<p>Thanks. This is my current code:</p>

<pre><code>protected void btnAdd_Click(object sender, EventArgs e) 
{
    listBox1.Items.Add(textBox3.Text);
    NumericUpDown1.Maximum = 100;
    NumericUpDown1.Minimum = 0;
    textBox5.Text = listBox1.Items.Count.ToString();
    if (NumericUpDown1.Value == 0) 
    { 
        NumericUpDown1.Value = +1;
    }
}
</code></pre>

<p><a href="http://i.stack.imgur.com/49AgO.png" rel="nofollow">As I've added two items to the basket the quantity should change to 2 but it doesn't it just stays at 1.</a></p>