.

C#
public class PersonsController : System.Web.Http.ApiController
{
    static Person[] s_persons = new Person[]
    {
        new Person() { Name = "John", Height=180},
        new Person() { Name = "Paul", Height=170}
    };

    
    public IEnumerable<Person> Get()   
    {
        return s_persons.ToArray();
    }
    
    public Person Get(int id)
    {
        return s_persons.Where(p => p.Id == id).FirstOrDefault();
    }

    public System.Net.Http.HttpResponseMessage Post(Person newPerson)
    {
        s_persons.Add(newPerson);

        // pass back to the caller success and new id (if database is used) 
        System.Net.Http.HttpResponseMessage result = new System.Net.Http.HttpResponseMessage(HttpStatusCode.OK);
        result.Headers.Location = new Uri("http://localhost:34460/api/persons/" + Convert.ToString(newPerson.Id));  // Id field would be autogenerated if database is used

        return result;
    }

    public void Put(Person personArg)
    {
        Person person = m_persons.Where(p => p.Id == personArg.Id).FirstOrDefault();
        person = personArg;
    }

    public void Delete(int id)
    {
        Person person = m_persons.Where(p => p.Id == id).FirstOrDefault();
        s_persons.Remove(person);
    }
}

Create App_Start folder.
Create WebApiConfig.cs under the folder.
http://myserver/api/persons will return list of all persons, because persons will be interpreted as PersonsController and a method starting with Get with no arguments will be used to return the data. {id} maps to id argument (in Get(int id)).

C#
using System.Web.Http;

namespace WebApiSimple
{
    public static class WebApiConfig
    {
        public static void Register(HttpConfiguration config)
        {
            config.Routes.MapHttpRoute(
                name: "DefaultApi",
                routeTemplate: "api/{controller}/{id}",
                defaults: new { id = RouteParameter.Optional }
            );
        }
    }
}

Create Global.asax file in the root of the project

C#
<%@ Application Codebehind="Global.asax.cs" Inherits="WebApiSimple.WebApiApplication" Language="C#" %>

and Global.asax.cs as well. These files will register mapping defined in WebApiConfig when the application starts.

C#
namespace WebApiSimple
{
    public class WebApiApplication : System.Web.HttpApplication
    {
        protected void Application_Start()
        {
            WebApiConfig.Register (System.Web.Http.GlobalConfiguration.Configuration);
        }
    }
}

type: http://myserver/api/persons to get list of persons
type: http://myserver/api/persons/1 to get person #1

HTML
<script src="http://ajax.aspnetcdn.com/ajax/jQuery/jquery-2.0.3.min.js"></script>
<script>
  function listAllPeople() 
  {
      $.getJSON('api/persons').done(
              function (people) 
              {
                  $.each(people, function (key, person) 
                  {
                      $('<li>', { text: person.Id + " " + person.Name } ).appendTo( $('#persons') );
                  });
              }
          );
  }
<script>

- Create a console app
- Inlude model.cs in the project

C#
HttpWebRequest myHttpWebRequest = (HttpWebRequest)HttpWebRequest.Create("http://localhost:34460/api/persons");
myHttpWebRequest.Method = "GET";
myHttpWebRequest.Credentials = System.Net.CredentialCache.DefaultCredentials;
myHttpWebRequest.ContentType = "application/json";
myHttpWebRequest.Accept = "application/json";

HttpWebResponse myHttpWebResponse = (HttpWebResponse)myHttpWebRequest.GetResponse();

// data in JSON format
System.IO.StreamReader myStreamReader = new System.IO.StreamReader(myHttpWebResponse.GetResponseStream());
string responseData = myStreamReader.ReadToEnd();

// deserialize the data
var p1 = new System.Web.Script.Serialization.JavaScriptSerializer().Deserialize<Person[]>(responseData);

- Create console app
- Include model.cs in the projects
- Right click on References, Add Reference, System.Net.Http 2.0 (for HttpClient)
- add reference to System.Net.Http.Formatting 4.0 (ReadAsAsync) As HttpClient calls are asynchronous, async-await" is used.

C#
  static void Main()
  {
      string baseAddress = "http://localhost:34460/";
      CallWebService(baseAddress + "api/persons").Wait();
  }

  static async Task CallWebService(string baseAddress)
  {
      HttpClientHandler handler = new HttpClientHandler();
      handler.UseDefaultCredentials = true;  // needed for Windows authentication
      
      using (HttpClient client = new System.Net.Http.HttpClient(handler))
      {
          client.BaseAddress = new Uri(baseAddress);
          
          client.DefaultRequestHeaders.Accept.Clear();
          client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

          // get all items
          HttpResponseMessage httpResponseMsg = await client.GetAsync("");
          if (httpResponseMsg.IsSuccessStatusCode)
          {
              Person[] person = await httpResponseMsg.Content.ReadAsAsync<Person[]>();
          }

          // get one item
          httpResponseMsg = await client.GetAsync(baseAddress+"/1");
          if (httpResponseMsg.IsSuccessStatusCode)
          {
              Person person = await httpResponseMsg.Content.ReadAsAsync<Person>();
          }

          // add new - Post
          Person newPerson = new Person() { Id=3, Name = "George" };
          httpResponseMsg = await client.PostAsJsonAsync("", newPerson);
          if (!httpResponseMsg.IsSuccessStatusCode) { return; }
          
          Uri newlyAddedPersonUrl = httpResponseMsg.Headers.Location;

          // update existing
          newPerson.Name = "Ringo";   
          await client.PutAsJsonAsync(newlyAddedPersonUrl, newPerson);

          // delete existing
          await client.DeleteAsync(newlyAddedPersonUrl);
      }
  }

C#
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/xml"));

-Navigate to Composer tab
-Select "POST" verb
-Enter web service address, e.g. http://myserver/api/persons
-In the Request body section, enter [{"Name": "John","Id":1}]
-Click "Execute"
If you set a break point in the Post() method, the Visual Studio will stop the web service execution there.

C#
[HttpGet]  
public IEnumerable<Person> RetrieveAll() {... }

[HttpPost]
public System.Net.Http.HttpResponseMessage Add(Person newPerson) {...}

[HttpPut]
public void Update(Person personArg) { ... }

[HttpDelete]
public void Remove(int id) { ... }

C#
// enables http://localhost:34460/apiaction/persons3/delete/1
config.Routes.MapHttpRoute(
    name: "ActionApi",
    routeTemplate: "apiaction/{controller}/{action}/{id}",   // prefix "apiaction" is different in order to avoid conflict with api/persons/1 and api/persons/action
    defaults: new { id = RouteParameter.Optional }
);
....
[HttpGet]
public void Delete(int id) 
{
    Person person = s_persons.Where(p => p.Id == id).FirstOrDefault();
    s_persons.Remove(person);
}

C#
public Person GetOne(int id)
{
    return s_persons.Where(p => p.Id == id).FirstOrDefault();
}
public Person GetByName(string name)
{
    return s_persons.Where(p => p.Name == name).FirstOrDefault();
}

You can call GetByName either http://myserver/api/persons3?name=john or http://myserver/apiaction2/persons3/getbyname/john. The latter requires routing like below:

C#
config.Routes.MapHttpRoute(
    name: "ActionApi2",
    routeTemplate: "apiaction2/{controller}/{action}/{name}",
    defaults: new { id = RouteParameter.Optional }
);

because web api maps {name} to the name of the method argument "name". If you change the argument to name1, the web api will not be able to route the apiaction2/persons3/getbyname/john. http://myserver/api/persons3?name=john will be then routed to GetAll() method that does not have any argument.