web api Route attribute not found
Install-Package AttributeRouting (for MVC)
Install-Package AttributeRouting.WebApi (for Web API)
Install-Package AttributeRouting.WebApi.Hosted (for self-hosted Web API)
Attribute Routing is native in ASP.NET MVC 5, or later, and ASP.NET Web API 2. check your MVC version it should be above the 4.