Could not load file or assembly 'System.Net.Http' or one of its dependencies

Question

Maybe Relevant information: I have a web application I built with .net 4.5. I wanted to deploy to Azure's Web Sites but it only supports .net 4.0 so I downgraded the project to .net 4.0. It still works when run locally.

When I publish to Azure, i get this error:

Could not load file or assembly 'System.Net.Http' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

I have tried removing the Web API with nuget and readding it, as another question on SO suggested but I still have the same problem.
I have tried close/open VS, and clean/build.

Answer 1

I solved a similar problem (System.Web.Http and System.Net.Http.Formatting) error by removing the reference to problem reference (which was pointed to my .Net installation folder) and replacing it with the reference file in my packages folder that was installed by the Microsoft.AspNet.WebApi NuGet package.

Answer 2

I had the same problem. However, updating assembly versions, copy local, and specific version settings alone did not solve my problem. In my application configuration I deploy a web and a worker role to a cloud service. After creating the service, on the configure tab I set the Operating System to Windows Server 2012 R2 to get the support for .Net Framework 4.5.1. But the error still occured.

Upon further research, I found that the *.cscfg file for my cloud service overrode the portal setting with an obscure osFamily setting of "3". When I started my project it was on MVC3 and did not yet have WebAPI and framework 4.5.1. osFamily 3 was the latest at the time.

In my latest deployment I had upgraded my site to 4.5.1 framework and MVC5. I verified it worked locally on my development machine. But it didn't work after deployment with the error referencing System.Net.Http.Formatting version 4.0.0.0 not being found. I later saw the deployment log that showed the source error

"The feature named NetFx451 that is required by the uploaded package is not available in the OS * chosen for the deployment."

Here is the blog article that led me to the solution to change the osFamily setting to 4. Then my site worked after a fresh deployment.

http://tech.trailmax.info/2014/02/azure-deployment-the-feature-named-netfx451-that-is-required-by-the-uploaded-package-is-not-available-in-the-os-chosen-for-the-deployment/