how to close data reader if it is open in other forms ,application

//This Is my data What ever m using
  SqlDataReader reader;

            DateTime dt1 = Convert.ToDateTime(dateTimePicker1.Text);
            DateTime dt2 = Convert.ToDateTime(dateTimePicker2.Text);

            SqlCommand cmd = new SqlCommand();
            cmd.Connection = getConnection();
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.CommandText = sp_name;

            SqlParameter P1 = new SqlParameter();
            P1.Direction = ParameterDirection.Input;
            P1.SqlDbType = SqlDbType.DateTime;
            P1.ParameterName = "@FromDate";
            P1.Value = dt1;
            cmd.Parameters.Add(P1);

            SqlParameter P2 = new SqlParameter();
            P2.Direction = ParameterDirection.Input;
            P2.SqlDbType = SqlDbType.DateTime;
            P2.ParameterName = "@ToDate";
            P2.Value = dt2;
            cmd.Parameters.Add(P2);
         
            reader = cmd.ExecuteReader();

//I Got error here that "Invalid attempt to call Read when reader is close"

            while (reader.Read())
            {
              

                DateTime dt = (DateTime)reader["TimeStamp"];         
                int milliSeconds = dt.Millisecond;
                s = dt.ToString("dd-MM-yyyy HH:mm:ss.fff");
                checkedListBox1.Items.Add(s);
                
            }
            return 0;