Type used as a variable error

I am making an application to store tickets for boarding a place for a imaginary airline. I have created a Ticket class see below

public class ticket
{
    String lastName;
    String firstName;
    String origin;
    String destination;
    String flightNumber;
    String seatNumber;
    String date;

    public ticket()
    {
    }

    public ticket(String lastname, String firstName, String origin, String destination,
        String flightNumber, String seatNumber, String date)
    {

    }

I have two ticket classes, first and economy. The plane can only hold 10 seats. So my structure is having two arrays of ticket objects, one containing 4 ticket objects "first class" and one containing 6 ticket objects "economy class". See below

 ticket[] ticketFirst = new ticket[4];
 ticket[] ticketEcon = new ticket[6];

I have to assign the seats randomly within their respective ticket arrays. I am calling my get method (example below) to check for duplicates, that is, that the randomly assigned seat is already filled or not.

public String getLastName() { return this.lastName; }

When I run my program I get the Error WindowsFormsApplication1.ticket' is a 'type' but is used like a 'variable' (relevant code below)

private void btnSubmit_Click(object sender, EventArgs e)
{
    Random random = new Random();
    int rand = random.Next(0, 4);
    if (ticket[rand].getLastName = null)
    {
        ticket[rand].setLastName = txbLastName.Text;
        ticket[rand].setFirstName = txbFirstName.Text;
        ticket[rand].setOrigin = txbOrigin.Text;
        ticket[rand].setDestination = txbDestination.Text;
        ticket[rand].setFlightNumber = txbFlightNumber.Text;
        ticket[rand].setSeatNumber = txbSeatNumber.Text;
        ticket[rand].setDate = txbDate.Text;
    }
    else
    {                
        MessageBox.Show("Seat Assignment Failed, try again.", "Seat Assignment");
    }
}

What my intention was is to assign the new ticket object a random seat (position) in the array, and most of my experience is with java. I think this is a syntax error from me using java-like syntax. Any pointers to get this to work properly?

Full Program Below

 using System;
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Data;
 using System.Drawing;
 using System.Linq;
 using System.Text;
 using System.Windows.Forms;

 namespace WindowsFormsApplication1
 {
 public partial class Form1 : Form
 {
    public Form1()
    {
        InitializeComponent();
        ticket[] ticketFirst = new ticket[4];
        ticket[] ticketEcon = new ticket[6];  

    }

    private void btnSubmit_Click(object sender, EventArgs e)
    {
        Random random = new Random();
        int rand = random.Next(0, 4);
        if (ticket[rand].getLastName = null)
        {
            ticket[rand].setLastName = txbLastName.Text;
            ticket[rand].setFirstName = txbFirstName.Text;
            ticket[rand].setOrigin = txbOrigin.Text;
            ticket[rand].setDestination = txbDestination.Text;
            ticket[rand].setFlightNumber = txbFlightNumber.Text;
            ticket[rand].setSeatNumber = txbSeatNumber.Text;
            ticket[rand].setDate = txbDate.Text;
        }
        else
        {                
            MessageBox.Show("Seat Assignment Failed, try again.", "Seat Assignment");
        }
    }
}

public class ticket
{
    String lastName;
    String firstName;
    String origin;
    String destination;
    String flightNumber;
    String seatNumber;
    String date;

    public ticket()
    {
    }

    public ticket(String lastname, String firstName, String origin, String destination,
        String flightNumber, String seatNumber, String date)
    {

    }

    public void setLastName(String lastName)
    {
        this.lastName = lastName;
    }

    public String getLastName()
    {
        return this.lastName;
    }

    public void setFirstName(String firstName)
    {
        this.firstName = firstName;
    }

    public String getFirstName()
    {
        return this.firstName;
    }

    public void setOrigin(String origin)
    {
        this.origin = origin;
    }

    public String getOrigin()
    {
        return this.origin;
    }

    public void setDestination(String destination)
    {
        this.destination = destination;
    }

    public String getDestination()
    {
        return this.destination;
    }

    public void setFlightNumber(String flightNumber)
    {
        this.flightNumber = flightNumber;
    }

    public String getFlightNumber()
    {
        return this.flightNumber;
    }

    public void setSeatNumber(String seatNumber)
    {
        this.seatNumber = seatNumber;
    }

    public String getSeatNumber()
    {
        return this.seatNumber;
    }

    public void setDate(String date)
    {
        this.date = date;
    }

    public String getDate()
    {
        return this.date;
    }
    }    
    }