GetOwinContext extension method is in the
System.Web.Http.Owin dll which needs to be downloaded as a nuget package (The nuget package name is Microsoft.AspNet.WebApi.Owin)
Nuget package here: https://www.nuget.org/packages/Microsoft.AspNet.WebApi.Owin
However, the method is still part of the
System.Net.Http namespace, so the
using definitions you have should be fine.
Okay, to clear up some confusion: If you are using an ApiController (i.e
MyController : ApiController) you will require the
If you are using a regular Mvc controller (i.e.
MyController : Controller) you will need the
In MVC 5 the pipelines for Api and regular MVC were very different, but often have the same naming conventions. So an extension method in one does not apply to the other. Same for a lot of the action filters etc.