C# ASP.NET Core 2.1/Entity Framework: Entity collention dosen't saving

Question

I have a simple ASP.NET Core (2.1) API that implements get & post methods with objects of this class:

public class Command
{
    public uint id { get; set; }
    public string command { get; set; }
    public List<Client> clients { get; set; }
}
public class Client
{
    public uint id { get; set; }
    public string nameofpc { get; set; }
}

public class CommandContext : DbContext
{
    public CommandContext(DbContextOptions<CommandContext> options) : base(options) { }

    public DbSet<Command> Commands { get; set; }
}

I send POST request with this entity:

var command = new Command()
{
    command = "/start^cmd.exe",
    clients = new List<Client>()
    {
        new Client()
        {
            nameofpc = "Zerumi"
        }
    }
};
// Converting to JSON and sending to api...

In CommandController.cs located this code:

[Route("api/[controller]")]
[ApiController]
public class CommandController : ControllerBase
{
    private readonly CommandContext _context;

    public CommandController(CommandContext context)
    {
        _context = context;
    }

    [HttpGet]
    public async Task<ActionResult<IEnumerable<Command>>> GetCommands()
    {
        return await _context.Commands.ToListAsync();
    }

    [HttpPost]
    public async Task<ActionResult<Command>> PostCommand([FromBody] Command item)
    {
        _context.Commands.Add(item);
        await _context.SaveChangesAsync();

        return CreatedAtAction(nameof(GetCommand), new { item.id }, item);
    }
}

The item parameter of the postcommand method is no different from what was sent. However, if i send GET request to /command after saving, i will get this:

[{"id":1,"command":"/start^cmd.exe","clients":null}]

Why colleсtion is null and what i need to do for good entity saving?

Answer 1

To me, it seems that something is missing, but maybe you configure stuff in OnModelCreating, hard to tell when I don't have your code. And you should use Pascal-casing in your EF-code and replace uint with int.

Then you should add DTO-classes (model-classes) for both Command and Client. Decorate each property in DTO with eg

[JsonProperty("command")]

in order to maintain correct casing (camel-casing).

public class Command
{
   public uint id { get; set; }
   public string command { get; set; }

   public List<Client> clients { get; set; }
}

public class Client
{
  public int CommandId { get; set; } // foreign key

  [ForeignKey(nameof(CommandId))]
  public Command Command { get; set; }

  public uint id { get; set; }
  public string nameofpc { get; set; }
}