ASP.NET Core Api parameter is null - asp.net-web-api

Question

I have an API controller which has actions to get and post data. and I am trying to access GetProductById meyhod from ajax bu productId parameter is always equals to zero (0). When I want to call GetAll method with GET method everything is fine.
JavaScript code is like below
var product = JSON.stringify({ productId: id });
$http({
method: 'POST',
contentType: 'application/json',
url: '/api/Product/ProductInfo',
data: product
}).then(function successCallback(response) {
console.log(response);
}, function errorCallback(response) {
console.log(response);
});
And API Controller is like below
[Route("api/Product")]
public class ProductController : BaseController
{
[HttpPost]
[Route("ProductInfo")]
public Product GetProductById([FromBody]int productId)
{
return UnitOfWork.GetRepository<Product>().FirstOrDefault(i => i.Id == productId);
}
[HttpGet]
[Route("GetAll")]
public string GetAll()
{
return "Can";
}
}
Can anyone say why that case is happening?

Answer 1

Although you are sending back a string representation of { productId: id } when the model is binded in the post method in the controller it is expecting an int. productId is barely the argument of that method, it doesn't define the parameter name you're supposed to send. Try sending just the id in the body instead of that json body { productId: id }.
If you want to send back a json body then the proper representation should be a class like the following for your post action
class ProductModel
{
int productId;
}
This would essentially make you able to parse your json payload the way you send it now, of course you can opt for custom model binders but that would be an overkill.
For example, if the id is 123 just use 123 as body, not { productId: 123 }