REST API - CreatedAtRoute method doesn't return a value - rest

Question

I'm building some REST API server in .NET Core and using Postman software to test it. I have a problem with POST method which doesn't return me any value ("Could not get any response") when I try to perform second Add operation on my DBContext class inside CreateUser method. My code :
UsersController :
[Produces("application/json")]
[Route("api/[controller]")]
public class UsersController : Controller
{
private readonly DBContext _context;
#region CONSTRUCTOR
public UsersController(DBContext context)
{
_context = context;
}
#endregion
#region HTTP GET
// GET: api/users || api/users?cardnr=xxx
[HttpGet]
public async Task<IActionResult> GetUsers(string cardNr)
{
if (String.IsNullOrEmpty(cardNr))
{
try
{
var users = await _context.Users.ToListAsync();
if (users.Any())
{
return Json(users);
}
else
{
return NotFound();
}
}
catch (Exception ex)
{
Helpers.ExceptionLogger.LogException(ex);
return StatusCode(500);
}
}
else
{
try
{
var user = await _context.Users.FirstOrDefaultAsync(u => u.Cards.Any(c => c.CardNumber.Equals(cardNr)));
if (user == null)
{
return NotFound();
}
else
{
return new ObjectResult(user);
}
}
catch (Exception ex)
{
Helpers.ExceptionLogger.LogException(ex);
return StatusCode(500);
}
}
}
//GET: api/users/1
[HttpGet("{id}", Name = "GetUserByID")]
public async Task<IActionResult> GetUserByID(Int32 id)
{
try
{
var user = await _context.Users.FirstOrDefaultAsync(u => u.IDUser == id);
if (user == null)
{
return NotFound();
}
else
{
return new ObjectResult(user);
}
}
catch (Exception ex)
{
Helpers.ExceptionLogger.LogException(ex);
return StatusCode(500);
}
}
#endregion
#region HTTP POST
[HttpPost]
public async Task<IActionResult> CreateUser([FromBody] Models.User userToCreate, string userGroupID)
{
if (userToCreate == null)
{
return BadRequest();
}
else
{
try
{
_context.Users.Add(userToCreate);
int parsingResult;
// if user passed userGroupID
if (userGroupID != null)
{
// parsing if userGroupID is a number
if (!int.TryParse(userGroupID, out parsingResult))
{
return BadRequest();
}
else
{
// if client want to assign a new user to some group
if (parsingResult > 0)
{
// creating new record in UserGroup table - assigning a user to group
var userGroup = new Models.UserGroup();
_context.Entry(userGroup).Property("IDGroup").CurrentValue = parsingResult;
_context.Entry(userGroup).Property("IDUser").CurrentValue = userToCreate.IDUser;
_context.UserGroups.Add(userGroup); // NOTE HERE
}
}
}
await _context.SaveChangesAsync();
return CreatedAtRoute("GetUserByID", new { id = userToCreate.IDUser }, userToCreate);
}
catch (Exception ex)
{
Helpers.ExceptionLogger.LogException(ex);
return StatusCode(500);
}
}
}
#endregion
}
User model :
public class User
{
[Key]
public int IDUser { get; set; }
[Required]
public string Name { get; set; }
public List<UserGroup> UsersGroups { get; set; }
}
UserGroup model :
public class UserGroup
{
public Group Group { get; set; }
public User User { get; set; }
}
DBContext class :
public class DBContext : DbContext
{
public DBContext(DbContextOptions<DBContext> options)
: base(options)
{
}
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
// shadow property - foreign key
modelBuilder.Entity<UserGroup>()
.Property<int>("IDUser");
// shadow property - foreign key
modelBuilder.Entity<UserGroup>()
.Property<int>("IDGroup");
modelBuilder.Entity<UserGroup>()
.HasKey( new string[]{ "IDUser", "IDGroup" });
modelBuilder.Entity<UserGroup>()
.HasOne(ug => ug.Group)
.WithMany(g => g.UsersGroups)
.HasForeignKey("IDGroup");
modelBuilder.Entity<UserGroup>()
.HasOne(ug => ug.User)
.WithMany(u => u.UsersGroups)
.HasForeignKey("IDUser");
base.OnModelCreating(modelBuilder);
}
public DbSet<Group> Groups { get; set; }
public DbSet<User> Users { get; set; }
public DbSet<UserGroup> UserGroups { get; set; }
}
The problem lies in HttpPost method in UsersController.
When I do "normal" POST and pass JSON object which contain a user to add without assigning it to group (empty userGroupID parameter) everything is ok - user gets added to the DataBase and Postman returns me a user with its ID.
screen :
and when I try to add a new user but with adding it to specific group I always get an error :
screen :
Even despite that error new user gets properly added to DB and associated with its group (record gets added to UserGroup table; UserGroup is join table between Users and Groups table). So I have proper data in my DB but I always get this error and I can't return new added user to client who called API and can't get his ID. Am I doing something wrong in my CreateUser method ?
UPDATE :
I have added a comment line in "NOTE HERE" in CreateUser method in UsersController. If I comment whole this line I don't get an error from Postman but obviously I don't get my User associated with its group (I don't get new record added to UserGroup join table). So it seems like another Add method on context object causing an error ... Does it make sense ?

Answer 1

Did you try to debug it?
Set a breakpoint on the row:
if (userToCreate == null)
Send again the request with Postman and debug your app. There you can see what and where it goes wrong.
Please let me know how it is going so I know how can I help you:)