按名称搜索，而不是ID

Question

I'm learning the Asp.net web api 2.0 and the current CRUD method just searches by id so I attempted to make it search by a title of a book but I've been unsuccessful.

What I added to the WebApiConfig.cs :

config.Routes.MapHttpRoute(
    name: "DefaultApi",
    routeTemplate: "api/{controller}/{name}",
    defaults: new { name = RouteParameter.Optional }
};

And the part I'm having trouble with:

// GET: api/Books/Name
[ResponseType(typeof(Book))]
public IHttpActionResult GetBook(string name)
{
    Book book = from a in db.Books where a.Title == name select a;

    if (book == null)
    {
        return NotFound();
    }
    else
    {
        return Ok(book);
    }
}

However it would let me build this, on the line where I'm trying to run the LINQ query I get an error of: Cannot implicitly convert type 'System.Linq.IQueryable<BookService.Models.Book>'to 'BookService.Models.Book'.

I tried changing the query around to be Book book = db.Books.Where(a => a.Title == name).AsQueryable(); but I still get the same error.

Answer 1

It returns a result set of IQueryable . Change

Book book = from a in db.Books where a.Title == name select a;

to

var books  = from a in db.Books where a.Title == name select a;

and then you need to iterate on the result set.

Or if you only need the first result set then you can use FirstoreDefault

Book book = db.Books.FirstOrDefault(a => a.Title == name);