How do I display my Json Objects on a web api?

Question

I am working on a ASP.NET Web Api and I'm having an issue figuring out how to display data to the api.

So to explain what I need to figure out. After accessing the objects from the Json file and converting JSON to a .NET type. I believe I should be able to display these on the api?

For example, whatever field I ask for, it should return the result sorted by that field. Now I need to display this data in different ports. For example.

https://host:port/api/books returns all unsorted (Book1-Book13)
https://host:port/api/books/id returns all sorted by id (Book1-Book13)
https://host:port/api/books/id/1 returns all with id containing '1' sorted by id (Book1, Book10-13)

I have followed this tutorial by microsoft and the application seems to be working in regards to starting and using different ports.

This is the code I have set up in my controller class BooksController.cs

 [Route("api/[controller]")]
[ApiController]
public class BooksController : ControllerBase
{
    [HttpGet]
    public ActionResult GetAllBooks()
    {
        string[] books = { "book1", "book2", "book3" };

        if (!books.Any())
            return NotFound();
        return Ok(books);
    }

    [HttpGet("id/{id}")]
    public string GetBookById(int id)
    {

        return $"book: {id}";
    }

    [HttpGet("author/{author}")]
    public string GetBookByAuthor(string author)
    {
        return $"author: {author}";
    }

This is my startup.cs

public class Startup
{
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
        GetAllBooks();
    }
    public IConfiguration Configuration { get; }

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddDbContext<TodoContext>(opt =>
                                           opt.UseInMemoryDatabase("TodoList"));
        services.AddControllers();
    }

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        app.UseHttpsRedirection();
        app.UseRouting();

        app.UseAuthorization();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllers();
        });
    }

    
    public void GetAllBooks()
    {
        string _path = $"C:\\Users\\filip\\source\\repos\\NexerGroupApi\\NexerGroupApi\\books.json";

        string jsonFromFile;
        using (var reader = new StreamReader(_path))
        {
            jsonFromFile = reader.ReadToEnd();
        }

        var booksFromJsonFile = JsonConvert.DeserializeObject<List<NexerGroupApi.Book>>(jsonFromFile);

        JArray bookArray = JArray.FromObject(booksFromJsonFile);

        IList<Book> bookList= bookArray.Select(p => new Book
        {
            Id = (string)p["Id"],
            Author = (string)p["Author"],
            Title = (string)p["Title"],
            Genre = (string)p["Genre"],
            Price = (string)p["Price"],
            Publish_date = (string)p["Publish_date"],
            Description = (string)p["Description"]
        }).ToList();
    }

    public class Book
    {
        public string Id { get; set; }
        public string Author { get; set; }
        public string Title { get; set; }
        public string Genre { get; set; }
        public string Price { get; set; }
        public string Publish_date { get; set; }
        public string Description { get; set; }
    }

I wonder where I actually set up my GetAllBooks() method so that I can then access them in the BooksController.cs and be able to do api/books/bookNameFromJsonFile and show that specific object with all of it's contents such as id, author, title, genre, etc.

I know that my IList<Book> bookList in the class startup.cs does not work, for some reason every variable get's null value. Although not sure why.

@mason Okay so I've been looking at a couple tutorials now - youtube.com/… - I will update my question and maybe you could answer to that? — filipman16
– filipman16, Commented Apr 22, 2021 at 17:18
You do not need to setup an individual route for every single book you have. You need to structure your route to have parameters. Check the documentation. — mason
– mason, Commented Apr 22, 2021 at 17:31
@mason Okay, I've checked out that link And a youtube video. As I understand it I then do for example [HttpGet("{id}")] and I then loop through my books in that method, then if I enter "api/book/2 it will retrieve the book where id=2. Does it work so that I can then do [HttpGet("{author}")] where I have a string author and so If I do api/books/authorname I will actually recieve the book/s from that author? — filipman16
– filipman16, Commented Apr 22, 2021 at 20:19
I edited the question to show you what I thought would work. Is there maybe an issue in my startup.cs that leads to this error code? — filipman16
– filipman16, Commented Apr 22, 2021 at 20:26
It's your route definitions. Like the error says, your route matches multiple endpoints. Most likely it's mad because it can't tell which action method to hit for a URL like /api/books/1, it doesn't know whether 1 is an Id or an Author. For GetBookByAuthor, you might change it to [HttpGet("author/{author}")], then someone who wished to look up books by author would hit the URL /api/books/author/Tom%20Clancy, and change GetBookById to [HttpGet("id/{id}")] so they can hit the URL /api/books/id/1. That makes it unambiguous. Just put some thought into how your structure the routes. — mason
– mason, Commented Apr 22, 2021 at 20:45

Chris L · Accepted Answer · 2021-04-23 10:48:13Z

1

As the error suggests, you have two routes that are ambiguous [HttpGet("{id}")] and [HttpGet("{author}")]

Given

When you hit api/books/1 the 1 could be the author or the bookid.

Consider changing the route of the author method to: [HttpGet("author/{author}")]

[HttpGet("{id}")]
public string GetBookById(int id)
{
    
    return $"book: {id}";
}

[HttpGet("author/{author}")] 
public string GetBookByAuthor(string author)
{
    return $"author: {author}";
}

So requests would route as follows:

api/books/1 would invoke GetBookById

api/books/author/jsmith would invoke GetBookByAuthor

Edit: Add list filtering:

To find a Book from the List<Book> then this can be done:

private readonly List<Book> _bookList; //populate this with books from json file

[HttpGet("{id}")]
public IActionResult GetBookById(int id)
{
    var book = GetBookObjectById(id);
    if(book is null) return NotFound();
    return Ok(book);
}

private Book GetBookObjectById(int id)
{
    return _bookList.FirstOrDefault(book => book.Id == id);
}

private Book GetBookObjectByAuthor(string author)
{
    return _bookList.FirstOrDefault(book => book.Author == author);
}

edited Apr 23, 2021 at 10:48

answered Apr 23, 2021 at 9:42

Chris L

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10 Comments

filipman16 Over a year ago

Thanks for the tip! I fixed this issue and have set up so that i can enter for example api/books/id/1 or api/books/title/bookTitle . One thing im wondering about now is the following.. I get my Json data from a file.json Where do I setup this to load all the data? In the end I want to be able to do api/books/bookNameFromJsonFile and show that specific object with all of it's contents such as id, author, title, genre, etc. If you look at my startup.cs I have set it up there and then you can see how my booksController.cs looks like, is this the wrong way?

filipman16 Over a year ago

I updated my question so If you check it out now you can see where I'm at and what's bothering me. I haven't been able to find anything that I can really understand yet.

Chris L Over a year ago

If this is just a learning exercise then I would personally just put the loadbook code you have in Startup.cs into the controller so it's created in the constructor. In a real world you'd make a BookService and inject it into the controller using dependency injection.

Chris L Over a year ago

Your json deserialise code can also be greatly improved - take a look at the microsoft docs here: learn.microsoft.com/en-us/dotnet/standard/serialization/…

filipman16 Over a year ago

This is more of a learning excercise than a real world scenario. I know I should be learning the correct way to begin with, but I have it easier learning this way then improving the code after I understand what I'm doing to begin with. Instead of just Ctrl+V everything. I have succesfully printed all the books now. But is there any way to print these as json objects? where id1 is in 1 {} and so on? This is how I display them public ActionResult GetAllBooks(){if (!bookList.Any())return NotFound(); return Ok(bookList);} but it's a complete hassle and cant be read.

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