OWin Startup attribute not found error on Web API REST Request - asp.net-web-api

I have a Web API project along with the built in help website. When I start up the project locally, the help website home page displays no problem. But when I send a REST POST request to an API controller using fiddler, I get the following response.
The following errors occurred while attempting to load the app.
- No assembly found containing an OwinStartupAttribute.
- No assembly found containing a Startup or [AssemblyName].Startup class.
To disable OWIN startup discovery, add the appSetting owin:AutomaticAppStartup with a value of "false" in your web.config.
To specify the OWIN startup Assembly, Class, or Method, add the appSetting owin:AppStartup with the fully qualified startup class or configuration method name in your web.config.
I have tried to solve using the suggestions in the error message but no joy.
It works OK on the test server.
Can anyone suggest why this error is returned only on a REST request and not when the help website starts up and any tips on how to solve?

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I have created Web API only. In that I want to use Elmah Logging. I have installed Nuget package of it. But when I try to access Elmah.axd file from browser it gives me an error : 404 Not Found. And that file is not generated. I have followed this link.
Do I need to do anything additional to generate/access this file?
I'm the author of the tutorial you have linked to. I just created a new Web API project and installed ELMAH. /elmah.axd is available. I would be very interested in seeing your web.config if you can update the question with that? Also, you can try to validate your web.config using the ELMAH Configuration Validator here: https://elmah.io/tools/configvalidator

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Finally I was able to narrow down the issue. This was happening because WebApiConfig.cs was getting registered twice

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I have a WCF that is hosted in an ASP.NET application. Suddenly, the WCF service has stopped working when i debug it in visual studio 2010. When i try to access the service, it throws the below exception.
CommunicationException was unhandled by user code. The remote server returned an error: NotFound
I have WCF tracing enabled but no errors are being logged.
The strange bit is that if i deploy the code to my QA server and access the application, the service works fine, so the code looks like not the problem.
If i also get the source code currently running in production successfully & try debugging it in my dev environment, it fails with the same error i mention above.
Any one have an idea what could be messed up in my dev environment?. I have tried both IE, Firefox & Chrome & the results are the same.
I after a very long debugging involving deleting Bin & obj folders and lots of rebuilds, i finally got this WCF service working again.
First, i suspected the service could be corrupted somehow, so i tried to update the service reference in my silverlight application but was bumped with the following error.
There was an error downloading 'http://localhost/mySite/Webservice/GetData.svc'.
The request failed with HTTP status 404: Not Found.
Metadata contains a reference that cannot be resolved: 'http://localhost/mySite/Webservice/GetData.svc'.
The remote server returned an unexpected response: (405) Method Not Allowed.
The remote server returned an error: (405) Method Not Allowed.
I then browsed to the physical folder path to confirm if really my .svc file was there and indeed as expected, the file was there.
Trying to Browse to the path http://localhost/mySite/Webservice/GetData.svc in my browser bumped me with another error below.
HTTP Error 404.7 - Not Found The request filtering module is
configured to deny the file extension.
Most likely causes: Request filtering is configured for the Web server
and the file extension for this request is explicitly denied.
This made me start thinking that suddenly, IIS 7.0 has decided to block access to my .svc files.
I then added fileExtension=".svc" mimeType="application/octet-stream" to IIS, restart IIS but got the same error.
I then read on some blog i cant remember about adding <add fileExtension=".svc" allowed="true" /> under <requestFiltering> tag in file applicationHost.config located at C:\Windows\System32\inetsrv\Config, still nothing changed. Tried adding <mimeMap fileExtension=".svc" mimeType="application/octet-stream" /> under serverSideInclude in the same file, again with no luck.
Tried this http://www.adamwlewis.com/articles/iis-7-not-serving-files-4047-error still with no luck.
The following 2 steps are i think what resolved the issue.
I added a mapping for the SVC extension to ASP.NET by running ServiceModelReg.exe -i from C:\Windows\Microsoft.NET\Framework\v3.0\Windows Communication Foundation
Browsed to my .svc file in the browser and this time it looked like i had made some progress but still, i had one more error to overcome . The is bellow.
Could not load type 'System.ServiceModel.Activation.HttpModule' from assembly 'System.ServiceModel, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
I resolved the above error by registering the correct version of ASP.NET using the ASP.NET IIS Registration Tool (aspnet_regiis.exe,) as described in the link below
https://msdn.microsoft.com/en-us/library/hh169179(v=nav.70).aspx
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I'm trying to set up an MVC application that will service several facebook applications for various clients. With help from Prabir's blog post I was able to set this up with v5.2.1 and it is working well, with one exception.
At first, I had only set up two "clients", one called DemoStore and the first client, ClientA. The application determines what client content and facebook settings to use based on the url. example canvasUrl: http://my_domain.com/client_name/
This works for ClientA, but for some reason when I try any DemoStore routes I get a 500 error. The error page points to an issue with the web.config.
Config Error:
Cannot add duplicate collection entry of type 'add' with unique key attribute 'name' set to 'facebookredirect.axd'
I am able to add additional clients with no problem, and changing DemoStore to something like "demo" while using the same facebook application settings works fine also.
Working calls:
http:// localhost:2888/ClientA/
http:// localhost:2888/ClientB/
http:// localhost:2888/Demo/
Failing call:
http:// localhost:2888/DemoStore/
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Any insight would be greatly appreciated.
I managed to figure out what went wrong here. Silly mistake..
After I had set up the application routes to require the client_name I changed the Project Url in the project properties to point to demostore by default. When I hit ctrl+S a dialog popped up that I promptly entered through without reading.
When I changed the Project Url, IIS Express created a new virtual directory for the project. This was the source of my problem. Why? I'm not sure, but once I removed the second site from my applicationhost.config I was able to access the DemoStore routes.
Moral of the story: read the VS dialog messages!

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I have an MVC3 project using nHibernate, Rhino and Castle. I finally got all of the components in place. I think. At least it runs and invokes the IWondsorContainer CreateContainer() method....after that method, the Application_Start does not fire and I get the message:
Server Error in '/' Application.
--------------------------------------------------------------------------------
The resource cannot be found.
Description: HTTP 404. The resource you are looking for (or one of its dependencies) could have been removed, had its name changed, or is temporarily unavailable. Please review the following URL and make sure that it is spelled correctly.
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