How to convert many records with same Name to a single records

here, i have fetched several Appointments with same Name according to the scheduled start and scheduled end date. Here, the condition is: if the booked records are scheduled in a sequential way(i.e. from 1-1-2018 to 2-1-2018 and other record is from 3-1-2018 to 4-1-2018). So, i want to convert these two records into one record from 1-1-2018 to 4-1-2018  and show on the web page using c#.
Right now, i am able to fetch all records from Appointment entity but not able to convert it into one record.
Therefore, i need help from you guys .