I'm trying to add HTMX to a project that uses Razor Pages and MVC controllers.
I have a form submitted by HTMX. It's handled by an MVC action, which returns a status code and empty response.
[Controller]
public class CustomerController : Controller
{
[HttpPost]
public async Task<IActionResult> CreateCustomer(CustomerDto dto)
{
// errors: return other status codes...
// success: return 204 for HTMX (not 200)
return NoContent();
}
}
The correct status code is returned, so the HTMX event handlers take appropriate action.
However the response always includes a body; specifically, 400...599 error pages. This particular action does not render a view, so I don't understand why it's happening.
What is the problem, and how do I fix it?
(ASP.NET Core v8)
That the response contains an error page was the hint I needed to resolve the issue.
I realised the configuration included the Status Code Pages middleware, with the UseStatusCodePagesWithReExecute option. So when returning a status code in the 400...599 range, the middleware would automatically re-execute the request and show a standard error page. One doesn't inspect the configuration often, so this was easy to forget / overlook.
I haven't read that docs page in years, but upon rereading it discovered that there's a nice feature to skip the middleware. The easiest is with an attribute on a Razor Pages page handler or MVC action. So in this case:
[SkipStatusCodePages]
[HttpPost]
public async Task<IActionResult> CreateCustomer(CustomerDto dto) { }
Now it returns the status code and an empty response, and HTMX can handle the rest.