Versioning Using Controllers

CustomControllerSelector

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Http;
using System.Web;
using System.Web.Http;
using System.Web.Http.Controllers;
using System.Web.Http.Dispatcher;

namespace Versioning
{
    public class CustomControllerSelector :DefaultHttpControllerSelector
    {
        private HttpConfiguration _config;
        public CustomControllerSelector(HttpConfiguration config): base(config)
        {
            _config = config;
        }

        public override HttpControllerDescriptor SelectController(HttpRequestMessage request)
        {
            var controllers = GetControllerMapping();
            var routeData = request.GetRouteData();
            var controllerName = routeData.Values["controller"].ToString();
            string versionNumber = "1";
            string customHeader = "X-EmployeesService-Version";
            if (request.Headers.Contains(customHeader))
            {
                versionNumber = request.Headers.GetValues(customHeader).FirstOrDefault();
            }
            if (versionNumber == "1")
            {
                controllerName = controllerName + "V1";
            }
            else
            {
                controllerName = controllerName + "V2";
            }
            HttpControllerDescriptor controllerDescriptor;
            if(controllers.TryGetValue(controllerName,out controllerDescriptor))
            {
                return controllerDescriptor;
            }
            return null;
        }


    }
}

EmployeeV1.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace Versioning.Models
{
    public class EmployeeV1
    {
        public int EmployeeID { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
    }
}

EmployeeV1Controller

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Web.Http;
using Versioning.Models;

namespace Versioning.Controllers
{
    public class EmployeeV1Controller : ApiController
    {
        EmployeeV1[] e1 = new EmployeeV1[]
        {
            new EmployeeV1(){EmployeeID =1, FirstName="DJ",LastName="Foo" },
            new EmployeeV1(){EmployeeID =2, FirstName="MJ",LastName="Koo" },
            new EmployeeV1(){EmployeeID =3, FirstName="RJ",LastName="Hoo" },

        };
        public IEnumerable<EmployeeV1> GetEmployees()
        {
            return e1;
        }
    }
}

EmployeeV2.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace Versioning.Models
{
    public class EmployeeV2
    {
        public int EmployeeID { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }

        public int Age { get; set; }

        public int Salary { get; set; }

    }
}

EmployeeV2Controller

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Web.Http;
using Versioning.Models;

namespace Versioning.Controllers
{
    public class EmployeeV2Controller : ApiController
    {
        EmployeeV2[] e1 = new EmployeeV2[]
       {
            new EmployeeV2(){EmployeeID =1, FirstName="DJ",LastName="Foo" ,Age=2,Salary=10},
            new EmployeeV2(){EmployeeID =2, FirstName="MJ",LastName="Koo",Age=3,Salary=20 },
            new EmployeeV2(){EmployeeID =3, FirstName="RJ",LastName="Hoo" ,Age=4,Salary=30},

       };
        public IEnumerable<EmployeeV2> GetEmployees()
        {
            return e1;
        }
    }
}

WebApiConfig

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web.Http;
using System.Web.Http.Dispatcher;

namespace Versioning
{
    public static class WebApiConfig
    {
        public static void Register(HttpConfiguration config)
        {
            // Web API configuration and services
            config.Services.Replace(typeof(IHttpControllerSelector), new CustomControllerSelector(config));
            // Web API routes
            config.MapHttpAttributeRoutes();

            config.Routes.MapHttpRoute(
                name: "DefaultApi",
                routeTemplate: "api/{controller}/{id}",
                defaults: new { id = RouteParameter.Optional }
            );
        }
    }
}