semesterWork/data/Repository/SQLGroupRepository.cs

using data.DAO;
using Microsoft.EntityFrameworkCore;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace data.Repository
{
    public class SQLGroupRepository : IGroupRepository
    {
        public readonly RemoteDatabaseContext dbContext;
        public SQLGroupRepository(RemoteDatabaseContext remoteDatabaseContext)
        {
            dbContext = remoteDatabaseContext;
        }
        public bool addGroup(GroupDAO group)
        {
            try
            {
                dbContext.groups.Add(group);
                return dbContext.SaveChanges() > 1;
            }
            catch (Exception ex) {
                return false;
            }
        }

        public IEnumerable<GroupDAO> getAllGroup()
        {
            try
            {
                return dbContext.groups.Include(group => group.Users).ToList();
            }
            catch (Exception ex) { 
                return new List<GroupDAO>();
            }
        }

        public bool addGroupWithStudents(GroupDAO groupDAO, IEnumerable<UserDAO> userDAOs)
        {
            using var transaction = dbContext.Database.BeginTransaction();
            try
            {
                dbContext.groups.Add(groupDAO);
                dbContext.SaveChanges();
                foreach (var item in userDAOs)
                {
                    item.Group = groupDAO;
                    dbContext.users.Add(item);
                }
                dbContext.SaveChanges();
                transaction.Commit();
                return true;
            } catch
            {
                transaction.Rollback();
            }
            return false;
        }

        public async Task<IEnumerable<GroupDAO>> getAllGroupAsync()
        {
            return await dbContext.groups.Include(group => group.Users).ToListAsync();
        }
    }
}