ASP.Net Core - How to get foreign key relation working on POST request for a web-api? - asp.net

Question

I am building a simple to-do list api using ASP.Net Core. It has two main two main models, a List model and a Task model. Each List has many Tasks. I build the models like this:
List Model:
namespace ToDoList.Models
{
public class List
{
[Key]
public int ListId { get; set; }
[Required]
[StringLength(25)]
public string Title { get; set; }
public string Colour { get; set; }
public virtual ICollection<Task> Tasks { get; set; }
public List()
{
Tasks = new List<Task>();
Colour = "secondary";
}
}
}
Task Model:
namespace ToDoList.Models
{
public class Task
{
[Key]
public int TaskId { get; set; }
[Required]
[StringLength(50)]
public string Title { get; set; }
public bool Done { get; set; }
public int ListId { get; set; }
public virtual List List { get; set; }
public Task()
{
Done = false;
}
}
}
When I send a post request to create a new task I am struggling to get the created task to be added to the Icollection part of the List model.
My Controller looks like this:
// POST: api/Tasks
[HttpPost]
public async Task<ActionResult<Models.Task>> PostTask(Models.Task task)
{
_context.Tasks.Add(task);
await _context.SaveChangesAsync();
return CreatedAtAction("GetTask", new { id = task.TaskId }, task);
}
If I send this data as JSON as a POST request:
{ title: "A New Task", listId: 11 }
I create this Task:
{"taskId":16,"title":"A New Task","done":false,"listId":11,"list":null}
As you can see it has the right listId but the list attached is null.
Also the task does not get added to the list.Tasks collection.
{"listId":11,"title":"Learn ASP.Net Core","colour":"secondary","tasks":[]}
As you can see tasks is still empty.
How do I get it set up that when ever a task is created it is always add to List.Tasks and then Tasks.List has the correct list attached to it, not null.
Also On my SQL Sever Database I expected to see a Tasks in the Lists table but I don't. Can anyone explain why?
SQL Sever Database Columns Picture

Answer 1

You could load the List entity from your DbContext and add it to the Task object you are returning:
[HttpPost]
public async Task<ActionResult<Models.Task>> PostTask(Models.Task task)
{
_context.Tasks.Add(task);
await _context.SaveChangesAsync();
task.List = _context.Lists.Single(task.ListId);
return CreatedAtAction("GetTask", new { id = task.TaskId }, task);
}
or you could return an instance of the Task loaded from the DbContext with included List:
var taskFromDb = _context.Tasks.Include(x => x.List).Single(x => x.Id = task.Id);
return CreatedAtAction("GetTask", new { id = task.TaskId }, taskFromDb);
To get a list with tasks, it needs to be loaded from the DbContext:
var listWithTasks = _context.Lists.Include(x => x.Tasks).Single(x => x.Id == task.ListId);