ComboBox与数据库绑定后同步问题

一个按纽 负责删除 ComboBox(手动连接数据库) 选中的内容
按完删除后, ComboBox 选中的内容没有被即时删除(数据库中已经删除)
等再一次打开软件后, ComboBox 刚刚选中的内容才被删除
按纽的代码:
       private void delete_Click(object sender, EventArgs e)
        {
                string str1 = "Data Source=.;Initial Catalog=prince;Integrated Security=True";
                try
                {
                    SqlConnection conn = new SqlConnection(str1);
                    conn.Open();
                    string sql = "delete from Song where Address=" +"'"+comboBox1.Text.ToString()+"'";
                    SqlCommand cmd = new SqlCommand(sql, conn);
                    int i = cmd.ExecuteNonQuery();
                    conn.Close();
                    if (i > 0)
                    {
                        MessageBox.Show("You Had Deleted" + comboBox1.Text.ToString());
                    }
                    else
                    {
                        MessageBox.Show("Delete fail");
                    }
                }
                catch (SystemException ex)
                {
                    MessageBox.Show("Error:" + ex.Message);
                }
        }
强调一下  ComboBox手动连接数据库