Getting this error I am displaying records in grid using ASP.NET MVC

using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using WebApplication2.Controllers;


namespace WebApplication2.Controllers
{
public class demoController : Controller
{
detailsEntities1 obj = new detailsEntities1();

public ActionResult Index()
{
return View();
}
public ActionResult webgrid()
{
var data = obj.personaldetails.ToList();
return View(data);

}


}
-----------------------------------------------------
@model IEnumerable< WebApplication2.Models.personaldetails>

@{
ViewBag.Title = "webgrid";
WebGrid grid = new WebGrid(Model,canSort:false,defaultSort:"firstname",rowsPerPage:3,
columnNames:new[]{"firstname","lastname"});
}
@grid.GetHtml(columns:grid.Columns(grid.Column("firstname",header:"firstname"),
grid.Column("lastname","lastname"),
grid.Column("id","id"),
grid.Column("active","active")))

webgrid

-----------------------------------

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


namespace WebApplication2.Models
{
    public class  personaldetails
    {
        public string id { set; get; }
        public string firstname { set; get; }
        public string lastname { set; get; }
        public string active { set; get; }
    }
}