List of elements in a model in .net core-CodePudding

I am trying to understand how models work in .net core and I run into the following problem: I have a model called blog:

public class Blog
{
    [Key]
    public int Id { get; set; }

    [Required(ErrorMessage = "Title is required")]
    [StringLength(40)]
    public string Title { get; set; }

    [Required(ErrorMessage = "Date is required")]
    [DisplayFormat(ApplyFormatInEditMode = true, DataFormatString = "{0:MM/dd/yyyy}")]
    public DateTime Date { get; set; }

    [Required(ErrorMessage = "Image is required")]
    public string Image { get; set; }

    [Required(ErrorMessage = "Description is required")]
    [StringLength(400)]
    public string Description { get; set; }

    public virtual IList<Paragraph> Paragraphs { get; set; } = new List<Paragraph>();

    [Required(ErrorMessage = "IsActive is required")]
    public bool IsActive { get; set; }

    [Required]
    public int? CompanyId { get; set; }
    public Company Company { get; set; }

    public Blog(){}
}

And the paragraph model:

    [Key]
    public int Id { get; set; }

    [Required(ErrorMessage = "Section is required")]
    public string Section { get; set;}

    [Required]
    public int? BlogId { get; set; }
    public Blog Blog { get; set; }

    public Paragraph()
    {
    }

And when executing the method that should bring me the data from this blog, it returns the list of empty paragraphs

    [HttpGet]
    [Route("api/[controller]/{id}")]
    public IActionResult GetById(int id)
    {
        var findBlog = _db.Blog.Find(id);
        if (findBlog == null)
        {
            return NotFound("Blog not found");
        }
        return new JsonResult(findBlog);
    }

The response:

{
"id": 6,
"title": "Test List",
"date": "2021-10-28T00:00:00",
"image": "https://images.pexels.com/photos/2489/street-building-construction-industry.jpg?auto=compress&cs=tinysrgb&dpr=2&w=500",
"description": "Desc",
"paragraphs": [],
"isActive": true,
"companyId": 1,
"company": null
}

CodePudding user response：

I suppose you are using Entity Framework Core. Then you need to load related data using include function.

for an example

using (var context = new BloggingContext())
{
    var blogs = context.Blogs
        .Include(blog => blog.Posts)
        .Include(blog => blog.Owner)
        .ToList();
}

for your case

 await _dbContext.Blogs
 .Include(blog => blog.Paragraphs)
 .FirstOrDefaultAsync(blog => blog.Id == id);

And to achieve this, you need to have proper relationships between entities.

See the SchoolContext here

CodePudding user response：

You can try to use .Inclue() to include the related data like below:

using Microsoft.EntityFrameworkCore;

var findBlog = _db.Blog.Include(a => a.Paragraphs).First(a => a.Id == id);
// all these ways can work well
//var findBlog = _db.Blog.Include(a => a.Paragraphs).Where(a => a.Id == id).ToList();
//var findBlog = _db.Blog.Include(a => a.Paragraphs).FirstOrDefault(a => a.Id == id);

Reference:

Eager Loading of Related Data