I've created a brand new Visual Studio 2019 web app using ASP.Net Core 3.1 with an MVC pattern.
My controller has an HttpPost method that should have an incoming Json object (I use [FromBody] for the incoming parameter).
No matter what I try, the incoming parameter is always Null. I've tried changing the parameter to a string, and modifying the Model to be a simple 3 field class, but it still comes in as a null.
I used Chrome's Developer Tools to make sure that my page is sending the Json object correctly from a JavaScript Post callback (and also used Postman to do the same) with the same result: my parameter is still Null.
What do I need to do to get the parameter to come in as an actual value?
My controller:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Newtonsoft.Json;
using canvasApiLib.API;
using CanvasGrades.Models.AuxiliaryModels;
namespace CanvasGrades.Controllers
{
public class FinalGradeController : Controller
{
public async Task<IActionResult> Index()
{
// Course Name
dynamic courseDetails = await clsCoursesApi.getCourseDetails(accessToken, apiUrl, canvasCourseId);
ViewData["CourseName"] = courseDetails.name;
// Course Term
dynamic courseTerm = await clsEnrollmentTermsApi.getEnrollmentTerm(accessToken, apiUrl, canvasAccountID, termNum);
ViewData["CourseTerm"] = courseTerm.name;
return View();
}
[HttpPost]
public async Task<IActionResult> LoadTable([FromBody]DTParameters dtParameters)
{
//DTParameters dtParameters = new DTParameters();
if (dtParameters == null)
{
dtParameters = new DTParameters();
}
}
}
}
My DTParameters model:
public class DTParameters
{
public int Draw { get; set; }
public DTColumn[] Columns { get; set; }
public DTOrder[] Order { get; set; }
public int Start { get; set; }
public int Length { get; set; }
public DTSearch Search { get; set; }
public IEnumerable<string> AdditionalValues { get; set; }
}
Most examples that I saw stated to tweak the app.UseMVC instantiation in the Configure call of the Startup.cs file, but mine doesn't have one:
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
services.AddDistributedMemoryCache();
services.AddControllersWithViews();
}
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
else
{
app.UseExceptionHandler("/Home/Error");
// The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
app.UseHsts();
}
app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseRouting();
app.UseAuthorization();
app.UseEndpoints(endpoints =>
{
endpoints.MapControllerRoute(
name: "default",
pattern: "{controller=Home}/{action=Index}/{id?}");
});
}
(ADDED)
{"draw":1,"columns":[{"data":"studentName","name":"","searchable":true,"orderable":true,"search":{"value":"","regex":false}},{"data":"studentEMail","name":"","searchable":true,"orderable":true,"search":{"value":"","regex":false}},{"data":null,"name":"","searchable":true,"orderable":true,"search":{"value":"","regex":false}},{"data":"finalGrade","name":"","searchable":true,"orderable":true,"search":{"value":"","regex":false}},{"data":"lastAttendDate","name":"","searchable":true,"orderable":true,"search":{"value":"","regex":false}},{"data":null,"name":"","searchable":true,"orderable":true,"search":{"value":"","regex":false}},{"data":null,"name":"","searchable":true,"orderable":true,"search":{"value":"","regex":false}},{"data":"bannerID","name":"","searchable":true,"orderable":true,"search":{"value":"","regex":false}},{"data":"crn","name":"","searchable":true,"orderable":true,"search":{"value":"","regex":false}}],"order":[{"column":0,"dir":"asc"}],"start":0,"length":10,"search":{"value":"","regex":false}}
I retried my simple parameter again, noticing that original ID field that I sent was an integer, but when I made it a string (like the Model stated) it came in with no issue.
public class SimpleParam
{
public string Id { get; set; }
public string Name { get; set; }
public string Foo { get; set; }
}
{"id": "1", "name": "fred", "foo": "bob"}
So, that means I'm going to have to figure out what's wrong with my DTParameters model.
The error is "dir": "asc". You need to either change this to an int ("dir": 0), or decorate the class property or the enumeration with
[JsonConverter(typeof(JsonStringEnumConverter))]
or put this in startup.cs
public void ConfigureServices(IServiceCollection services)
{
services
.AddControllers()
.AddJsonOptions(options =>
options.JsonSerializerOptions.Converters.Add(new JsonStringEnumConverter())
);
//...
}
Your input beautified:
{
"draw": 1,
"columns": [
{
"data": "studentName",
"name": "",
"searchable": true,
"orderable": true,
"search": {
"value": "",
"regex": false
}
}
],
"order": [
{
"column": 0,
"dir": "asc"
}
],
"start": 0,
"length": 10,
"search": {
"value": "",
"regex": false
}
}
Your Datatables classes with correct decoration (See above DTOrderDir):
public class DTParameters
{
public int Draw { get; set; }
public DTColumn[] Columns { get; set; }
public DTOrder[] Order { get; set; }
public int Start { get; set; }
public int Length { get; set; }
public DTSearch Search { get; set; }
public IEnumerable<string> AdditionalValues { get; set; }
}
public class DTColumn
{
public string Data { get; set; }
public string Name { get; set; }
public bool Searchable { get; set; }
public bool Orderable { get; set; }
public DTSearch Search { get; set; }
}
public class DTOrder
{
public int Column { get; set; }
public DTOrderDir Dir { get; set; }
}
[JsonConverter(typeof(JsonStringEnumConverter))]
public enum DTOrderDir
{
ASC,
DESC
}
public class DTSearch
{
public string Value { get; set; }
public bool Regex { get; set; }
}
Read here for more info: JavaScriptSerializer - JSON serialization of enum as string
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