Below you'll see the source code of the file. Note that we're just showing the main part, and hiding some parts of the file which are not relevant for understanding the essentials. Click to expand the code

@inherits Custom.Hybrid.Razor14
@{
  // Tell the page that we need the 2sxc Js APIs
  Kit.Page.Activate("2sxc.JsCore"); 
}
<!-- unimportant stuff, hidden -->

App.Query WebApi Examples In this... <!-- unimportant stuff, hidden -->

@{
  var authorId = AsDynamic(App.Data["Persons"].First()).EntityId;
}
<button type="button" class="btn btn-primary" onclick="getAuthor(this, @authorId)">
  Get Author #@authorId
</button> 

<script>
  function getAuthor(moduleContext, authorId) {
    $2sxc(moduleContext).webApi.fetchJson('authorsquery/get?authorId=' + authorId)
      .then(function (author) {
        alert('Found author: '
          + author.FirstName + ' ' + author.LastName 
          + ' (with ' + author.Books.length + ' books) \n\n'
          + 'The raw JSON: \n' + JSON.stringify(author)
        );
      });
  }

</script>

<!-- unimportant stuff, hidden -->

Note about Hybrid WebAPIs

These examples are all done to work in both Dnn ☢️ and Oqtane 💧. Because of this, the Api Controller have special conditional statements like #if NETSTANDARD which uses different namespaces in .net core and .net Framework.
If you only target Dnn or Oqtane, you can remove the lines you don't need. See See how to use #if

Source Code of /api/AuthorsQueryController.cs

// Add namespaces for security check in Oqtane & DNN despite differences in .net core/.net Framework
// If you only target one platform, you can remove the parts you don't need
#if NETCOREAPP
using Microsoft.AspNetCore.Authorization; // .net core [AllowAnonymous] & [Authorize]
using Microsoft.AspNetCore.Mvc;           // .net core [HttpGet] / [HttpPost] etc.
#else
using System.Web.Http;                    // .net 4.5 [AllowAnonymous] / [HttpGet]
using DotNetNuke.Web.Api;                 // [DnnModuleAuthorize] & [ValidateAntiForgeryToken]
#endif
using System.Linq;                        // this enables .First() or .Select(x => ...)
using Dynlist = System.Collections.Generic.IEnumerable<dynamic>;

// Tutorial note: This is used in the WebApi demos App.Query

[AllowAnonymous]                          // all commands can be accessed without a login
[ValidateAntiForgeryToken]                // protects API from users not on your site (CSRF protection)
public class AuthorsQueryController : Custom.Hybrid.Api14 // see https://r.2sxc.org/CustomWebApi
{
  [HttpGet]                               // [HttpGet] says we're listening to GET requests
  public dynamic Get(int authorId)
  {
    var query = App.Query["AuthorsWithBooks"];
    query.Params("AuthorId", authorId.ToString());
    var a = AsDynamic(query["Current"].First());

    return new {
        Id = a.EntityId,
        a.FirstName,
        a.LastName,
        Picture = a.Mugshot,
        Books = AsList(query["CurrentBooks"])
          .Select(b => new {
            Id = b.EntityId,
            b.Title
          })
      };
  }

}

// The next line is for 2sxc-internal quality checks, you can ignore this
// 2sxclint:disable:no-dnn-namespaces - 2sxclint:disable:no-web-namespace