Wednesday, January 22, 2014

HTTP Error 405 When Making a PUT or DELETE Call to Web API Service

If you build ASP.NET Web API services and are testing against IIS, you might encounter the following error when trying to execute a HTTP PUT or DELETE:
Error Summary:

HTTP Error 405.0 - Method Not Allowed

The page you are looking for cannot be displayed because an invalid method (HTTP verb) is being used.

Searching the web actually yielded a ton of results but as usual they were wide and plentiful making it difficult to discern the correct solution. I'm using VS.NET 2012 and VS.NET 2013 on Windows 7 and Windows 8 (variations of these), so this solution is current.

Here it is: a combination of updating the values for a few of the HTTP Handlers and modules in the web.config will solve this issue. 1st the solution, which resides within the <system.webServer> section within the web.config file for the Web API project:

  <validation validateIntegratedModeConfiguration="false" />
  <remove name="WebDAVModule" />
  <remove name="WebDAV" />
  <remove name="ExtensionlessUrlHandler-ISAPI-4.0_32bit" />
  <remove name="ExtensionlessUrlHandler-ISAPI-4.0_64bit" />
  <remove name="ExtensionlessUrlHandler-Integrated-4.0" />
  <add name="ExtensionlessUrlHandler-ISAPI-4.0_32bit" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" modules="IsapiModule" scriptProcessor="%windir%\Microsoft.NET\Framework\v4.0.30319\aspnet_isapi.dll" preCondition="classicMode,runtimeVersionv4.0,bitness32" responseBufferLimit="0" />
  <add name="ExtensionlessUrlHandler-ISAPI-4.0_64bit" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" modules="IsapiModule" scriptProcessor="%windir%\Microsoft.NET\Framework64\v4.0.30319\aspnet_isapi.dll" preCondition="classicMode,runtimeVersionv4.0,bitness64" responseBufferLimit="0" />
  <add name="ExtensionlessUrlHandler-Integrated-4.0" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" />

The explanation:

  1. The default ExtensionlessUrlHandler-* handlers displayed above are set within the %userprofile%\documents\iisexpress\config\applicationhost.config file and do not by default allow HTTP PUT and DELETE verbs. By removing and re-adding the handlers with all of the HTTP verbs we will allow, processing will continue as expected.
  2. Unfortunately updating the handlers is not enough. The WebDAV HTTP Publishing feature will block HTTP PUT and DELETE calls regardless of our previous modifications. WebDAV is a feature allowing access to files and folders via the internet as an alternative to FTP. If you are not using it in the Web API project, then removing the module will free up the restriction on these HTTP verbs. If you want to read more about what WebDAV is, please read this.
After these modifications have been made try using Fiddler or Postman and make a HTTP PUT or DELETE call and it should now work as expected. If you are reading this and are using a HTTP POST for all operations and bypassing a good RESTful design by having multiple POST actions on a controller (only distinguished by the action name in the URL as opposed to the verb defining the route), reconsider and try these modifications if in their absence had previously prevented you from creating that rich RESTful service you initially set out to make.

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