How do I Dispose a HttpResponseMessage in my Web Api Method?

Question

I'm getting the CA2000 error on all my Wep Api 2 controllers for the Options() verb.

In method 'PromotionController.Options()', object '<>g__initLocal0' is not disposed along all exception paths.

I need to support pre-flight requests made for cross domain ajax calls so all I'm doing is returning a HttpStatusCode.Ok so that the subsequent post/put/delete will fire off.

public HttpResponseMessage Options()
{
    return new HttpResponseMessage { StatusCode = HttpStatusCode.OK };
}

I have tried the using statement like this:

public HttpResponseMessage Options()
{
    using(var response = new HttpResponseMessage())
    {
        response.StatusCode = HttpStatusCode.OK;
        return response;
    }
}

but when I hit it with an Options request from Postman I get an exception:

Cannot access a disposed object.\r\nObject name: 'System.Net.Http.HttpResponseMessage'.

How do I return the HttpStatusCode.Ok in a way that it won't throw Code Analysis errors?

Thanks!

See [this previous answer](http://stackoverflow.com/questions/11361912/how-do-i-dispose-of-resources-after-an-asp-net-web-api-request-completes) and [this one](http://stackoverflow.com/q/27715327/1260204) — Igor, Apr 01 '16 at 19:04
@Igor I saw that post while searching but from what I can see, HttpResponseMessage doesn't support RegisterForDispose. Only HttpRequestMessage does. — Elliott, Apr 01 '16 at 19:19

score 4 · Answer 1 · edited Dec 15 '16 at 17:30

You can register the response object for disposing using RegisterForDispose method of HttpRequestMessage class. Infrastructure of .Net will disposes all registered object after disposing the request.

I can't guaranty that you won't get the error after that, but the object will be disposed so that you can suppress the error.

Example:

HttpResponseMessage response = Request.CreateResponse();
// Do what you need with response
// ...
// ...
request.RegisterForDispose(response);// response will be disposed by host

score 2 · Accepted Answer · edited May 23 '17 at 12:30

2

Exception about accessing a disposed object is obvious because when execution leaves the using block, response is disposed, but you're returning it out of the using block and out of the method. You can't access that object outside of the method, because it simply doesn't exist anymore.

In general, to solve the CA2000 warning simply dispose the instance of HttpResponseMessage class explicitly when you don't need it anymore.

In your case solution could be to override the Dispose method of your controller (implements the ApiController method) and explicitly dispose your instances there. Check for example this question.

You can also just suppress the warning and instance will be disposed later by the garbage collector anyway. But it's not a proper solution.

edited May 23 '17 at 12:30

Community

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answered Apr 01 '16 at 19:01

David Ferenczy Rogožan

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I'm hoping they'res another way because I hate suppressing warnings – Elliott Apr 01 '16 at 19:21
Yep, I definitely agree and what I read in answers linked in Igor's comment to your question, you should have at least 2 possibilities - controller's `Dispose` method and `RegisterForDispose` extension. – David Ferenczy Rogožan Apr 01 '16 at 19:23
@Elliott Did my answer helped you to solve your problem? If yes, can you accept it so others will be able to find the answer more easily, please? It would also allow others to mark similar questions as a duplicate of this one. – David Ferenczy Rogožan Jun 16 '16 at 16:10
@Elliott Thank you! – David Ferenczy Rogožan Jun 16 '16 at 17:13

How do I Dispose a HttpResponseMessage in my Web Api Method?

2 Answers2