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

public class UserModel
{
 public string UserID { get; set; }
 public string UserName { get; set; }
}

public class UserController : ApiController
{
 public UserModel getAdmin()
 {
  return new UserModel() { UserID = "000", UserName = "Admin" };
 } 
}

$.ajax({
 type: 'GET',
 url: 'api/user/getadmin',
 dataType: 'json',
 success: function (data, textStatus) {
  alert(data.UserID + " | " + data.UserName);
 },
 error: function (xmlHttpRequest, textStatus, errorThrown) {
 }
});

public bool add(UserModel user)
{
 return user != null;
}

<input type="button" name="btnOK" id="btnOK" value="发送POST请求" />

$('#btnOK').bind('click', function () {
 //创建ajax请求，将数据发送到后台处理
 var postData = {
  UserID: '001',
  UserName: 'QeeFee'
 };
 $.ajax({
  type: 'POST',
  url: 'api/user/add',
  data: postData,
  dataType: 'json',
  success: function (data, textStatus) {
   alert(data);
  },
  error: function (xmlHttpRequest, textStatus, errorThrown) {
  }
 });
});