How to return HTTP 429?

Question

I'm implementing an API using WCF and the specification says to return HTTP 429 in certain circumstances.

Normally I'd simply write:

throw new WebFaultException(HttpStatusCode.NotFound);

However the HttpStatusCode enum does not contain a 429.

I can obviously cast to the enum

throw new WebFaultException((HttpStatusCode)429);

However I'm worried that this will not produce the correct result to the application calling my API.

What's the best way to create extend the HttpStatusCode and send valid (but unsupported) HTTP statuses?

Found this loosely-related link. It doesn't answer the question but might provide background: http://stackoverflow.com/questions/2022887/how-can-i-createa-custom-http-status-code-from-a-wcf-rest-method — TypeIA, Mar 25 '14 at 14:05
What kind of specification requires to send an unregistered status code? — Julian Reschke, Mar 25 '14 at 15:21
@JulianReschke if you check the HTTP spec 429 is indeed a valid code - it's just .NET doesn't support have it in the enum — Liath, Mar 25 '14 at 15:26
@Liath: Julian works on the HTTP spec. :-) http://tools.ietf.org/html/rfc6585#section-4 is the proposal for HTTP/429. — EricLaw, Mar 25 '14 at 20:25
@JulianReschke while 429 Too Many Requests isn't mentioned in RFC 2616, it is mentioned in RFC 6585. FWIW, while I haven't used it with WCF, I have found that in ASP.NET setting `HttpResponse.StatusCode` to 429 resulted in the correct number, but not the correct string, so it's necessary to also set `StatusDescription`, or to just set `Status`. I'd worry WCF could end up with a similar partially-correct result due it hitting on the same bit of code that ASP.NET does. — Jon Hanna, Mar 25 '14 at 20:26
everybody: sorry, I forgot that 429 is indeed are registered code! — Julian Reschke, Mar 26 '14 at 06:46

score 56 · Accepted Answer · answered Mar 25 '14 at 20:18

56

From the C# Language Specification 5.0:

The set of values that an enum type can take on is not limited by its enum members. In particular, any value of the underlying type of an enum can be cast to the enum type and is a distinct valid value of that enum type.

So this is completely alright to do and would be your best bet:

throw new WebFaultException((System.Net.HttpStatusCode)429);

answered Mar 25 '14 at 20:18

Derek W

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It is alright from a language perspective, but it doesn't mean the API will handle it properly... – Thomas Levesque Mar 25 '14 at 20:21
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The exception here is being thrown from the API. It is the callers responsibility to handle that exception. – Derek W Mar 25 '14 at 20:25
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Thanks for this. I wanted to return "Locked" 423. Good to know that casting will work. – John Henckel Apr 19 '16 at 17:49
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I can confirm that this type of cast works just fine in .NET Framework 4.8, where "TooManyRequests" is not explicitly defined in the HttpStatusCode enum -- Just in case anyone visiting this post is unclear. – Paul Karkoska Sep 02 '20 at 17:33
Today I Learned – Jaans Dec 04 '20 at 14:56

score 2 · Answer 2 · answered Dec 15 '21 at 03:45

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In case somebody is using the webApi template, in which the controller is returning an IActionResult object.

return new StatusCodeResult(429);

That worked for me.

answered Dec 15 '21 at 03:45

diegocl02

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score 0 · Answer 3 · answered Mar 25 '14 at 19:16

If you are hosting the WCF service with IIS you can turn on ASP.Net Compatibility Mode. With that done you can set the status of HttpContext.Current.Response.StatusCode to 429.

With that said. I think your best bet is to try casting the 429 to HttpStatusCode and seeing what happens. If that works then you can save yourself the headache.

score -3 · Answer 4 · answered Nov 26 '19 at 08:26

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You can use HttpStatusCode directly

HttpStatusCode.TooManyRequests

answered Nov 26 '19 at 08:26

Teepi

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Hi Teepi - can you add a little more information? Has the enum been updated since I posted the question or is this a different one? – Liath Nov 26 '19 at 13:04
This is the actual HttpStatusCode enum – Teepi Nov 28 '19 at 09:41
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does not exist in .net 4.7.2, might want to add what version you are using. – Edwin Stoteler Dec 19 '19 at 12:23
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Framework up to 4.8 doesn't have 429 enumerated, but it's present in .NET Framework 5.0 Preview 7. It was added to Standard and Core in 2.1. – Joe Cullinan Jul 29 '20 at 23:13

How to return HTTP 429?

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