Demo/Domain/UseCase/GroupUseCase.cs

using Posechaemost.Data.LocalData.Entity;
using Posechaemost.Data.Repository;
using Posechaemost.Domain.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Posechaemost.Domain.UseCase
{
    public class GroupUseCase
    {
        private GroupRepositoryImpl _repositoryGroupImpl;

        public GroupUseCase(GroupRepositoryImpl repositoryGroupImpl)
        {
            _repositoryGroupImpl = repositoryGroupImpl;
        }

        public List<Group> GetAllGroups() => _repositoryGroupImpl.GetAllGroups()
            .Select(it => new Group { Id  = it.Id, Name = it.Name}).ToList();        

        public Group UpdateGroupName(String name, String name1) {
            GroupLocalEntity? result = _repositoryGroupImpl.UpdateGroup(name);
            if (result == null) throw new Exception("");
            Group? group = GetAllGroups().FirstOrDefault(it => it.Name == result.Name);
            if (group == null) throw new Exception("");
            return new Group {Id = group.Id, Name = name1};
        }
        public GroupLocalEntity AddGroup(String name, String id) 
        {
            return _repositoryGroupImpl.AddGroup(name, id);
        }
    }
}