Net Core 5.0 Web API HttpPut - [FromBody]- how to omit some parameters in JSON

Question

Hello,

I have developped a .Net Core 5.0 Web API and I pass the following json as [FromBody] parameters to update the book in database and it updates successfully.

id=> 1

[FromBody] parameters=>

{

"Title": "Sun",

"Description": "store sun",

"Genre": "man",

"CoverUrl": "www.CCC.fr"

}

But when I want to only update "Title", "Description", "CoverUrl" and pass the following json as [FromBody] parameters. After the updates, I found the data is not correct in the database because the other information "Genre" is set to ""...(In the database, Id=>1, "Title"=>"Sun to update", "Description"=>"","Genre"=>"", "CoverUrl"=>"")

id=> 1

[FromBody] parameters=>

{

"Title": "Sun to update"

"Description": null,

"CoverUrl": ""

}

Is there a way to only update "Title" "Description", "CoverUrl" without changing the other information "Genre" via [FromBody], thanks in advance.

This is the BooksController.cs=>

namespace books.Controllers

{

[Route("api/[controller]")]

[ApiController]

public class BooksController : ControllerBase

{ 

    public BooksService _booksService;

    public BooksController(BooksService booksService)

    {

        _booksService = booksService;

    }

    [HttpPut("{id}")]

    public IActionResult UpdateBookById(int id, [FromBody]Book book)

    {

        var updatedBook = _booksService.UpdateBookById(id, book);

        return Ok(updatedBook);

    }

}

}

This is the book.cs=>

public class Book

{

    public int Id { get; set; }

    public string Title { get; set; }

    public string Description { get; set; }

    public string Genre { get; set; }

    public string CoverUrl { get; set; }

} 

This is the BooksService.cs=>

public class BooksService

{

    private AppDbContext _context;

    public BooksService(AppDbContext context)

    {

        _context = context;

    }

    public Book UpdateBookById(int bookId, Book book)

    {

        var _book = _context.Books.FirstOrDefault(n => n.Id == bookId);

        if(_book != null)

        {

            _book.Title = book.Title;

            _book.Description = book.Description;

            _book.Genre = book.Genre;

            _book.CoverUrl = book.CoverUrl;

            _context.SaveChanges();

        }

        return _book;

    }

}

Answer 1

The coalesce operator should be a good fit for this situation.

?? and ??= operators - the null-coalescing operators

if(_book != null)
{
    _book.Title = book.Title ?? _book.Title;
    _book.Description = book.Description ?? _book.Description;
    _book.Genre = book.Genre ?? _book.Genre;
    _book.CoverUrl = book.CoverUrl ?? _book.CoverUrl;
    _context.SaveChanges();
}