MapToVersion.cs

namespace HomeController
{
    [ApiVersion("1.0")]
    [Route("api/Values")]
    public class HomeController : Controller
    {
        [HttpGet]
        public IEnumerable<string> Get()
        {
            return new string[] { "Value1 from Version 1", "value2 from Version 1" };
        }
    }

    [ApiVersion("2.0")]
    [Route("api/Values")]
    public class HomeV2Controller : Controller
    {
        public IEnumerable<string> Get()
        {
            return new string[] { "value1 from Version 2", "value2 from Version 2" };
        }

        [HttpGet, MapToApiVersion("3.0")]
        public IEnumerable<string> GetV3()
        {
            return new string[] { "value1 from Version 3", "value2 from Version 3" };
        }
    }
}