This short article shows you how to resolve the error “The type or namespace name ‘IHttpActionResult’ could not be found”.
If you have an ASP.NET is not create using Web API temp and you include the Web API controller in your project then you might get the following error:
Severity Code Description Project File Line Source
Error CS0246 The type or namespace name ‘IHttpActionResult’ could not be found (are you missing a using directive or an assembly reference?) WebApplication1 C:\VCShapeTemp\WebApplication1\WebApplication1\Controllers\TriviaController.cs 38 IntelliSense
You go to pull down menu choose Tools -> NuGet Package Manager -> Manage NuGet Package for Soluttion…
Search for webapi then pick the newest, I use 5.2.3.