Pass listBox2 to Form2

[ms.chips]

I am working on a class assignment and I'm stuck. I would like to copy listBox2(from Form1) to listBox3(from Form2). The code I have now compiles, but it does not copy the listBox2 to listBox3. Also, when I click btnAdd in Form2 is adds txtnewcourse.txt(from Form2) to listBox2(from Form1) not listBox3(from Form2) like it should. Here is my code:

public partial class Form1 : Form
{

    public Form1()
    {
        InitializeComponent();
    }

    private void btnSelect_Click(object sender, EventArgs e)
    {
        foreach (object x in listBox1.SelectedItems)
            listBox2.Items.Add(x);
    }

    private void btnClearSelection_Click(object sender, EventArgs e)
    {
        listBox1.SelectedIndex = -1;
    }

    private void btnDeleteSelected_Click(object sender, EventArgs e)
    {
        if (listBox1.SelectedIndex != -1)
        //The following foreach causes an error because every x depends on the SelectedItems, but, it is changing.
        //foreach (object x in listBox1.SelectedItems)
        //    listBox1.Items.Remove(x);
        {
            int thisMany = listBox1.SelectedItems.Count;
            object[] mySelection = new object[thisMany];

            listBox1.SelectedItems.CopyTo(mySelection, 0); //'0' means copy from the first selected item

            foreach (object x in mySelection)
                listBox1.Items.Remove(x);
        }
    }

    private void btnempty_Click(object sender, EventArgs e)
    {
        DialogResult choice;
        choice = MessageBox.Show("Are you sure to clear the selected choices?", "Clear Selected Choices", MessageBoxButtons.YesNo);
        if (choice == DialogResult.Yes)
        {
            listBox2.Items.Clear();
        }
    }

    private void btnGoForm2_Click(object sender, EventArgs e)
    {
        Form2 form2 = new Form2();
        form2.Lbox = listBox2;
        form2.ShowDialog();
    }

}

public partial class Form2 : Form
{
    private ListBox listbox;
    public ListBox Lbox
    {
        set
        {
            this.listbox = value;
        }
        get
        {
            return this.listbox;
        }
    }
    public Form2()
    {
        InitializeComponent();
    }


    private void Form2_Load(object sender, EventArgs e)
    {
        txtNewCourse.Focus();
        listBox3= this.listbox;   
    }

    private void btnAdd_Click(object sender, EventArgs e)
    {
        string value = txtNewCourse.Text.ToString();
        if (listBox3.Items.Contains(value))
            MessageBox.Show(txtNewCourse.Text + " already exists in the list.", "Duplicate entry", MessageBoxButtons.OK, MessageBoxIcon.Error);
        else if(txtNewCourse.Text == "")
             MessageBox.Show("Please enter a course.", "Empty textbox", MessageBoxButtons.OK, MessageBoxIcon.Error);
        else
        {
            listBox3.Items.Add(txtNewCourse.Text);
            txtNewCourse.Focus();
        }
    }
}

}