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Asked: 2026-06-01T03:09:44+00:00

I want to implement the recently approved PATCH HTTP verb in a RESTful service

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I want to implement the recently approved PATCH HTTP verb in a RESTful service implemented with ASP MVC 3. I have added the following settings in the web.config file.

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <system.webServer>
        <handlers>
            <add name="PATCHVerbHandler" path="*" verb="PATCH" modules="ProtocolSupportModule" requireAccess="None" /> 
        </handlers>
        <security>
            <requestFiltering>
                <verbs>
                    <add verb="PATCH" allowed="true" />
                </verbs>
            </requestFiltering>
        </security>
    </system.webServer>
</configuration>

The action method is decorated with the AcceptVerbs("PATCH") attribute.

The service works properly with the PATCH verb. The URL gets routed to the right action method and returns the proper data.

The strange issue is if I using a different URL that does not match any routes using the PATCH verb, IIS returns “200 OK” instead of “404 Not Found”. All the standard verbs (GET, PUT, DELETE, POST, HEAD, OPTIONS) do not have this problem.

Do I need to register additional handlers for the PATCH verb or is it a routing issue? Any help is appreciated.

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1 Answer

  1. Editorial Team

    You don’t actually need a custom handler to process HTTP requests made with the PATCH verb; instead, you may want to keep decorating your actions with the AcceptVerbs("PATCH") attribute while checking that the ASP.NET ISAPI is configured to handle any verb (it is the default), including PATCH.

    If you have to handle this kind of requests using a custom module, by the way, please keep in mind that it is the responsibility of the handler itself to set the status code for each request (including the ones it should handle, according to the mapping, but it can’t for whatever reason) and maybe it is not setting the correct value upon finishing.

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