to add combo box items from Sql DB in c#.net

combobox    textbox
  Items      price
  sss         100
  ddd         140
  fff         220

private void Form4_Load(object sender, EventArgs e)
        {
            con = new SqlConnection("data source=PC\\SQLEXPRESS;integrated security=true;Initial catalog=MyDB");
            BindData1();
}
 public void BindData1()
        {
            

            con.Open();
            string strCmd = "select Items from tblbill";
            SqlCommand cmd = new SqlCommand(strCmd, con);
            SqlDataAdapter da = new SqlDataAdapter(strCmd, con);
            DataSet ds = new DataSet();
            da.Fill(ds);
            cmd.ExecuteNonQuery();
            con.Close();

            comboBox1.DisplayMember = "items";
            comboBox1.ValueMember = "items";
            comboBox1.DataSource = ds.Tables[0];

            comboBox1.Enabled = true;

        }

 private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
           
            con.Open();
           string sel = comboBox1.SelectedItem.ToString();
            
            
           
           SqlCommand cmd = new SqlCommand("select price from tblbill where items=" + comboBox1.SelectedValue, con);
            
            SqlDataReader dr = cmd.ExecuteReader();
            while (dr.Read())
            {
                p = dr[0] as string;
                //department = reader[1] as string;
                
            }
            
            textBox1.Text = p;
            con.Close();
        }