multi level Hierarchical Grid Load On Demand with ASP.NET MVC ignite is throwing error "Object reference not found" when we call BindChild method.

View:

@(Html.Infragistics().Grid(Model))

Controller:

using System.Web.Mvc;
using System.Collections.Generic;
using Infragistics.Web.Mvc;
using Recon.Models;

namespace Recon.Controllers
{
public class TestController : Controller
{
public ActionResult List()
{
GridModel grid = CreateGridModel();
return View(grid);
}

private GridModel CreateGridLoadOnDemand()
{
GridModel grid = CreateGridModel();
grid.ID = "gridLoadOnDemand";
grid.LoadOnDemand = true;
grid.DataSourceUrl = this.Url.Action("BindParent");
grid.ColumnLayouts[0].DataSourceUrl = this.Url.Action("BindChild");
grid.ColumnLayouts[0].ColumnLayouts[0].DataSourceUrl = this.Url.Action("BindInnerChild");
return grid;
}

// Take grid creation outside as it will be used in all methods:
private GridModel CreateGridModel()
{
GridModel grid = new GridModel();

// Set up properties and columns:
grid.AutoGenerateColumns = false;
grid.PrimaryKey = "CustomerID";
grid.Columns = new List<GridColumn>();
grid.Columns.Add(new GridColumn("Customer", "CustomerID", "string", "300px"));
grid.Columns.Add(new GridColumn("Company Name", "CompanyName", "string", "150px"));
grid.Columns.Add(new GridColumn("Country", "Country", "string", "150px"));
grid.AutoGenerateLayouts = false;

// Create child layout
GridColumnLayoutModel layout = new GridColumnLayoutModel();
layout.Key = "Orders";
layout.ForeignKey = "CustomerID";
layout.PrimaryKey = "OrderID";
layout.AutoGenerateColumns = false;

layout.Columns = new List<GridColumn>();
layout.Columns.Add(new GridColumn("Order ID", "OrderID", "number", "100px"));
layout.Columns.Add(new GridColumn("Customer", "CustomerID", "string", "100px"));
layout.Columns.Add(new GridColumn("Order Date", "OrderDate", "date", "150px"));
layout.Columns.Add(new GridColumn("Shipped Date", "ShippedDate", "date", "150px"));

// Create child layout
GridColumnLayoutModel layout2 = new GridColumnLayoutModel();
layout2.Key = "Orders";
layout2.ForeignKey = "OrderID";
layout2.PrimaryKey = "SupplierID";
layout2.AutoGenerateColumns = false;

layout2.Columns = new List<GridColumn>();
layout2.Columns.Add(new GridColumn("Supplier ID", "SupplierID", "number", "100px"));
layout2.Columns.Add(new GridColumn("Order ID", "OrderID", "number", "100px"));
layout2.Columns.Add(new GridColumn("Supplier Name", "SupplierName", "string", "100px"));

//add that layout to the grid
layout.ColumnLayouts.Add(layout2);
grid.ColumnLayouts.Add(layout);

// Add paging to child layouts (different from the parent's)
GridPaging layoutPaging = new GridPaging();
layoutPaging.VisiblePageCount = 2;
layoutPaging.PageSize = 5;
//layoutPaging.Type = OpType.Remote;
layout.Features.Add(layoutPaging);

//And lastly set ID so the client widget can be normally interacted with (see the events in the view)
grid.ID = "hierarchicalGrid";
//most importantly turn Load On demand on and define response Urls:
grid.LoadOnDemand = true;
grid.DataSourceUrl = this.Url.Action("BindParent");
grid.ColumnLayouts[0].DataSourceUrl = this.Url.Action("BindChild");
grid.ColumnLayouts[0].ColumnLayouts[0].DataSourceUrl = this.Url.Action("BindInnerChild");

var dataContext = new NorthwindDataContext();
var dataSource = dataContext.Customers;
var ds = dataSource.Take(30);
grid.DataSource=ds;

//Add features:
GridSorting sorting = new GridSorting();
sorting.Type = OpType.Remote;
grid.Features.Add(sorting);
GridPaging paging = new GridPaging();
paging.PageSize = 10;
paging.Type = OpType.Remote;
grid.Features.Add(paging);

// Return the finished model
return grid;
}

public JsonResult BindParent()
{
//create a model
GridModel grid = CreateGridModel();

//set its data source
var dataContext = new NorthwindDataContext();
var dataSource = dataContext.Customers;
grid.DataSource = dataSource.Take(30);
//and use the GetData() method to return the results
return grid.GetData();
}

public JsonResult BindChild(string path, string layout)
{
//create a model
GridModel grid = CreateGridModel();
//set its data source
var dataContext = new NorthwindDataContext();
var dataSource = dataContext.Orders;
grid.DataSource = dataSource;
//and use the GetData() method to return the results
return grid.GetData(path, layout);
}

public JsonResult BindInnerChild(string path, string layout)
{
//create a model
GridModel grid = CreateGridModel();
//set its data source
var dataContext = new NorthwindDataContext();
var dataSource = dataContext.Orders;
grid.DataSource = dataSource;
//and use the GetData() method to return the results
return grid.GetData(path, layout);
}
}

}