C＃将子表单上的整个列表框数据发送到父表单上的列表框

Question

我有两个表单，从子表单中我有一个列表框，它通过同一表单上的其他内容获取信息。我希望能够将该列表框中的所有信息发送到主/父表单上的列表框中。通过按钮单击带有标记来发回信息。 在儿童表格上：

private void btnToMain_Click(object sender, EventArgs e)
    {
        //send info back to Main to be placed in listBoxMain
        if (listBoxChild.Items != null)
        {
            foreach ( string item in listBoxChild.Items)
//I'm not sure what should go here to get all of the items to return
//I think it should be part of my ClassItem which is a class
            this.Tag = this.listBoxChild.SelectedItem as ClassItem;
            this.DialogResult = DialogResult.OK;
        }

    }

在主/父表格上：

private void btnFormChild_Click(object sender, EventArgs e)
    {
        //open new child form
        Form2 child = new Form2();
        //receive info
        if (child.ShowDialog() == DialogResult.OK)
        {
            ClassItem d = child.Tag as ClassItem; //ClassItem is a public class
            if (d != null)
            {
                //put info into listbox
                listBoxMain.Items.Add(d);
            }

        }
    }