I try to add a city with a country name, database add new country with a new country id-CodePudding

I got some error but I couldnt fix it. I want to add a new city with a country name but country id (if exists) will not change in database(it wont add with a new id).

Here is my City class;

 [Table("Cities")]
    public class City
    {
        [Key]
        public int Id { get; set; }

        [Required]
        [StringLength(30)]
        public string Name { get; set; }

        [ForeignKey("Countries")]
        public int CountryId { get; set; }
        public  Country Country { get; set; }
    }

And here is my Country class;

[Table("Countries")]
    public class Country
    {
        [Key]
        public int Id { get; set; }

        [Required]
        [StringLength(30)]
        public string Name { get; set; }

        public  ICollection<City> Cities { get; set; }
    }

I used CQRS and Mediator design patterns.

This is my Create Command;

 public class CreateCityCommand : IRequest<City>
    {
        public City City { get; set; }
    }

This is my Create Command Handler;

public class CreateCityCommandHandler : IRequestHandler<CreateCityCommand, City>
    {
        private readonly EssoContext _context;

        public CreateCityCommandHandler(EssoContext context)
        {
            _context = context;
        }

        public async Task<City> Handle(CreateCityCommand request, CancellationToken cancellationToken)
        {
            var check = await _context.City.FirstOrDefaultAsync(c => c.Name == request.City.Name);

            if (check != null)
            {
                throw new InvalidOperationException("You cannot add the same value!!!");
            }

            _context.City.Add(request.City);
            await _context.SaveChangesAsync();
            return request.City;
        }
    }

And here is my controller;

[HttpPost("Create")]
        public async Task<ActionResult<City>> PostCity([FromBody] City city)
        {
            try
            {
                var command = new CreateCityCommand() { City = city };
                var result = await _mediator.Send(command);
                return Ok(result);
            }
            catch(Exception ex)
            {
                return StatusCode((int)HttpStatusCode.InternalServerError, ex.Message);

            }
            
        }

This is swagger output (seeing countries)

Every city has a country, and each country may have many cities. That's why i used CountryId and property (as FK) in City class. In country class, i defined collection(list) of cities. But I dont know what is the problem. Thanks for help...

CodePudding user response：

As per my understanding you want to get related city data with country

public class GetCountriesCommand: IRequest<IEnumerable<Country>>{

}
public class GetCountriesCommandHandler : IRequestHandler<GetCountriesCommand, IEnumerable<Country>>
    {
        private readonly EssoContext _context;

        public GetCountriesCommandHandler(EssoContext context)
        {
            _context = context;
        }

        public async Task<IEnumerable<Country>> Handle(GetCountriesCommand command, CancellationToken cancellationToken)
        {
            // .Includes helps to return the related cities for all countries
            return await _context.Country.Include(x=>x.City).ToListAsync();
        }
    }

In country controller

[HttpGet("Get-Countries")]
        public async Task<IActionResult<IEnumerable<Country>>> Get()
        {
            try
            {
                var command = new GetCountriesCommand();
                var result = await _mediator.Send(command);
                return Ok(result);
            }
            catch(Exception ex)
            {
                return StatusCode((int)HttpStatusCode.InternalServerError, ex.Message);
            }
            
        }

CodePudding user response：

I guess I figured it out. I just declared CountryId as a foreign key. That's why each CountryId has many cities.

I did city class like that;

 [Table("Cities")]
    public class City
    {
        [Key]
        public int Id { get; set; }

        [Required]
        [StringLength(30)]
        public string Name { get; set; }

        public int CountryId { get; set; }
        
    }

Did I correct?