Jqgrid in MVC 3 using helpers and adding the dll of Jqgrid

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Hi ,
I am trying to implement JqGrid in MVC3 using helpers, but all the time i get a javascript error -"JavaScript runtime error: Object doesn't support property or method 'jqGrid'".I also add reference of MVCJqgrid in my project.
Here is my code for Jqgrid in view :-

@(Html.Grid("AgentGrid")
    .SetCaption("Agents")

    .AddColumn(new MvcJqGrid.Column("AgentId").SetLabel("Agent SSN"))
        .AddColumn(new MvcJqGrid.Column("Name"))
        .AddColumn(new MvcJqGrid.Column("Country"))
        .AddColumn(new MvcJqGrid.Column("City"))
        .AddColumn(new MvcJqGrid.Column("Title"))
        .SetUrl(Url.Action("List", "Home"))
    .SetAutoWidth(true)
    .SetRowNum(10)
    .SetViewRecords(true)
    .SetPager("pager")
    )

and here is my code of action in controller:-

public ActionResult List(GridSettings gridSettings)
       {
           DataContext db = new DataContext();

           string Name = string.Empty;
           string Country = string.Empty;
           string City = string.Empty;
           string Title = string.Empty;

           if (gridSettings.IsSearch)
           {
               Name = gridSettings.Where.rules.Any(r => r.field == "Name") ?
                      gridSettings.Where.rules.FirstOrDefault(r => r.field == "Name").data : string.Empty;
               Country = gridSettings.Where.rules.Any(r => r.field == "Country") ?
               gridSettings.Where.rules.FirstOrDefault(r => r.field == "Country").data : string.Empty;
               City = gridSettings.Where.rules.Any(r => r.field == "City") ?
              gridSettings.Where.rules.FirstOrDefault(r => r.field == "City").data : string.Empty;
               Title = gridSettings.Where.rules.Any(r => r.field == "Title") ?
              gridSettings.Where.rules.FirstOrDefault(r => r.field == "Title").data : string.Empty;

           }

           var Agents = db.Agent.ToList();
           int totalAgents = Agents.Count;
           var jsonData = new
           {
               total = totalAgents / gridSettings.PageSize + 1,
               page = gridSettings.PageIndex,
               records = totalAgents,
               rows = (
                       from c in Agents
                       select new
                       {
                           id = c.AgentId,
                           cell = new[]
                   { c.AgentId.ToString(),
                       string.Format("{0} {1}", c.Name, c.Country),
                       c.City,
                       c.Title
                   }
                       }).ToArray()
           };

           return Json(jsonData, JsonRequestBehavior.AllowGet);
       }

Please suggest me for resolve the issue !!
Thanks in advance!!