C#

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

        private void button1_Click(object sender, EventArgs e)
        {
            Customer customer=new Customer(this.textBox1.Text, this.textBox2.Text);

            this.listBox1.Items.Add(customer.firstName);
        }

        private void listBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            Customer cust=(Customer)listBox1.SelectedItem;

            this.asdfStatusStripPanel.Text=cust.firstName+" "+cust.lastName;
        }
    }

    public class Customer
    {
        public string firstName;
        public string lastName;

        public Customer(string FirstName, string LastName)
        {
            firstName = FirstName;
            lastName = LastName;
        }
    }
}

public int GetAvailableMemory()
{
    PerformanceCounter ramCounter;
    ramCounter = new PerformanceCounter("Memory", "Available MBytes");

    int a=Convert.ToInt32(ramCounter.NextValue());

    return a;
}