ASP.NET Core Web API - Put action with DTO didn't update the existing object

Question

I've been trying to write Put (update) action without the id property, by using DTO. But every time I'm trying I'm getting the existing object and not the updated one, and I can't figure out why and how to change it so it will work.

My repository:

public User Update(Guid id, User user)
{
   var userToUpdate=_context.Users.FirstOrDefault(x => x.Id == id);
   _context.Entry(userToUpdate).State = EntityState.Modified;
   _context.SaveChanges();
   return userToUpdate;
}

My DTO:

public class UserPostDTO
{
    public UserPostDTO()
    {

    }
    public UserPostDTO(User user)
    {
        UserName= user.UserName;
        Password= user.Password;
        LastLogin= user.LastLogin;
    }
    [StringLength(255)]
    public string UserName { get; set; } = null!;
    [StringLength(255)]
    public string Password { get; set; } = null!;
    [Column(TypeName = "datetime")]
    public DateTime? LastLogin { get; set; }
    public User ToPostUser()
    {
        var user = new User();
        user.UserName = UserName;
        user.Password = Password;
        user.LastLogin = LastLogin;
        return user;
    }
}

My Controller:

public class UserController : ControllerBase
{
    private readonly IUserRepository _userRepository;
    public UserController(IUserRepository userRepository)
    {
        _userRepository = userRepository;
    }

    [HttpPut("{id}")]
    public IActionResult Put(Guid id, [FromBody] UserPostDTO user)
    {
        _userRepository.Update(id, user.ToPostUser());
        return Ok();
    }

Yong Shun · Accepted Answer · 2022-07-24 07:11:33Z

1

Didn't see you updating the User object with the new value.

Probably this is what you need:

public User Update(Guid id, User user)
{
    var userToUpdate = _context.Users.FirstOrDefault(x => x.Id == id)
        .AsNoTracking();
    if (userToUpdate == null)
    {
        // Handle ID is not existed
        throw new ArgumentNullException("ID is not existed");
    }

    user.Id = userToUpdate.Id;
    _context.Entry(user).State = EntityState.Modified;
    _context.SaveChanges();
    return user;
}

edited Jul 24, 2022 at 7:11

answered Jul 23, 2022 at 13:25

Yong Shun

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2 Comments

Inbar Manor Over a year ago

Thanks for your help, but It's not working well. but when I'm writing this code I'm getting this errpr: The instance of entity type 'User' cannot be tracked because another instance with the same key value for {'Id'} is already being tracked. When attaching existing entities, ensure that only one entity instance with a given key value is attached. Consider using 'DbContextOptionsBuilder.EnableSensitiveDataLogging' to see the conflicting key values.

Yong Shun Over a year ago

Hmmm, the exception message is a bit broad, maybe you can try to remove the tracking graph from userToUpdate with .AsNoTracking() as it is used to validate whether the record is existed. This post may help for solving your current issue.

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