Missing ADO.NET entity data model template from visual studio 2012 professional

This MSDN thread explains how to fix it.

To summarize:

• Either disable incremental linking, by going to

  Project Properties 
     -> Configuration Properties 
         -> Linker (General) 
            -> Enable Incremental Linking -> "No (/INCREMENTAL:NO)"
  

• or install VS2010 SP1.

Edits (@CraigRinger): Note that installing VS 2010 SP1 will remove the 64-bit compilers. You need to install the VS 2010 SP1 compiler pack to get them back.

This affects Microsoft Windows SDK 7.1 for Windows 7 and .NET 4.0 as well as Visual Studio 2010.

The steps I needed to perform were:

1. Add reference to System.Web.Http.WebHost.
2. Add App_Start\WebApiConfig.cs (see code snippet below).
3. Import namespace System.Web.Http in Global.asax.cs.
4. Call WebApiConfig.Register(GlobalConfiguration.Configuration) in MvcApplication.Application_Start() (in file Global.asax.cs), before registering the default Web Application route as that would otherwise take precedence.
5. Add a controller deriving from System.Web.Http.ApiController.

I could then learn enough from the tutorial (Your First ASP.NET Web API) to define my API controller.

App_Start\WebApiConfig.cs:

using System.Web.Http;

class WebApiConfig
{
    public static void Register(HttpConfiguration configuration)
    {
        configuration.Routes.MapHttpRoute("API Default", "api/{controller}/{id}",
            new { id = RouteParameter.Optional });
    }
}

Global.asax.cs:

using System.Web.Http;

...

protected void Application_Start()
{
    AreaRegistration.RegisterAllAreas();

    RegisterGlobalFilters(GlobalFilters.Filters);
    WebApiConfig.Register(GlobalConfiguration.Configuration);
    RegisterRoutes(RouteTable.Routes);
    BundleConfig.RegisterBundles(BundleTable.Bundles);
}

Update 10.16.2015:

Word has it, the NuGet package Microsoft.AspNet.WebApi must be installed for the above to work.