slarny4/Demo1/Data/Repository/GroupRepositoryImpl.cs

// C:\Users\adm\Source\Repos\presence1\Demo\Data\Repository\GroupRepositoryImpl.cs
using System.Collections.Generic;
using System.Linq;
using Demo.Data.Exceptions;
using Demo.Data.LocalData;
using Demo.Data.LocalData.Entity;
using Demo.Data.RemoteData.RemoteDataBase;

namespace Demo.Data.Repository
{
    public class GroupRepositoryImpl : IGroupRepository
    {
        private RemoteDatabaseContext context;

        public GroupRepositoryImpl(RemoteDatabaseContext context)
        {
            this.context = context;
        }

        public void AddGroup(Group group)
        {
            if (LocalStaticData.Groups.Any(g => g.Id == group.Id))
                throw new RepositoryException("Group with the same ID already exists.");
            LocalStaticData.Groups.Add(group);
        }

        public void DeleteGroup(int id)
        {
            var group = GetGroupById(id);
            LocalStaticData.Groups.Remove(group);
        }

        public IEnumerable<Group> GetAllGroups()
        {
            return LocalStaticData.Groups;
        }

        public Group GetGroupById(int id)
        {
            var group = LocalStaticData.Groups.FirstOrDefault(g => g.Id == id);
            if (group == null)
                throw new GroupNotFoundException(id);
            return group;
        }

        public void UpdateGroup(Group group)
        {
            var existingGroup = GetGroupById(group.Id);
            existingGroup.Name = group.Name;
        }
    }
}