Service class with db context

I have implemented service which working with db context. I am using entity framework and I do not need repositories because logic is quite simple.

I want to keep simple logic but clean approach. One problem I have is when I want to call service method 2 times in same service instance. I will get context dispose exception. this is not problem in my case because for now I do not have case like that. But maybe you have idea for better solution.

my code:

using Common.Configurations;
using Common.Container;
using Common.Factory;
using Common.Helpers;
using Common.Services;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using RemoteManager.EntityFramework;
using Common.Entities;

namespace RemoteManagerApi.Services
{
    public class MachineService : IMachineService
    {
        private readonly IOptions<ApplicationConfiguration> applicationConfiguration;
        private readonly ILogger<MachineService> logger;
        private readonly IMachineCleaner machineCleaner;
        private readonly IFileContainer fileContainer;
        private readonly RemoteManagerContext context;

        public MachineService(RemoteManagerContext context, IFileContainerFactory fileContainerFactory, IOptions<ApplicationConfiguration> applicationConfiguration, IMachineCleaner machineCleaner, ILogger<MachineService> logger)
        {
            this.fileContainer = fileContainerFactory.CreateContainer();
            this.applicationConfiguration = applicationConfiguration;
            this.logger = logger;
            this.machineCleaner = machineCleaner;
            this.context = context;
        }

        public async Task<MachineConfiguration> Add(MachineConfiguration machine)
        {
            try
            {
                await this.fileContainer.CreateDirectory(machine.SessionFolder);
                logger.LogInformation($"Start  {nameof(MachineService)}:{nameof(this.Add)}");
                using (var db = this.context)
                {
                    var res = db.MachineConfigurations.Add(machine);
                    db.SaveChanges();
                    return await Task.FromResult(res);
                }
            }
            catch
            {
                logger.LogError($"Error  {nameof(MachineService)}:{nameof(this.Add)}");
                throw;
            }
        }

        public async Task<bool> Delete(int id)
        {
            try
            {
                logger.LogInformation($"Start  {nameof(MachineService)}:{nameof(this.Delete)}");
                using (var db = this.context)
                {
                    var machineConfiguration = db.MachineConfigurations.FirstOrDefault(f => f.Id == id);
                    var isDeleted = db.MachineConfigurations.Remove(machineConfiguration);
                    db.SaveChanges();
                    return await Task.FromResult(true);
                }
            }
            catch
            {
                logger.LogError($"Error  {nameof(MachineService)}:{nameof(this.Delete)}");
                throw;
            }
        }

        public async Task<MachineConfiguration> Get(int id)
        {
            try
            {
                logger.LogInformation($"Start  {nameof(MachineService)}:{nameof(this.Get)}");
                using (var db = this.context)
                {
                    var machineConfiguration = db.MachineConfigurations.FirstOrDefault(f => f.Id == id);
                    return await Task.FromResult(machineConfiguration);
                }
            }
            catch
            {
                logger.LogError($"Error  {nameof(MachineService)}:{nameof(this.Get)}");
                throw;
            }
        }

        public async Task<IEnumerable<MachineConfiguration>> GetAll()
        {
            try
            {
                logger.LogInformation($"Start  {nameof(MachineService)}:{nameof(this.GetAll)}");
                using (var db = this.context)
                {
                    var machineConfigurations = db.MachineConfigurations.ToList();
                    return await Task.FromResult(machineConfigurations);
                }
            }
            catch
            {
                logger.LogError($"Error  {nameof(MachineService)}:{nameof(this.GetAll)}");
                throw;
            }
        }
    }
}