An exception of type 'System.NullReferenceException' occurre

Question

using DemoGrids.Models;

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.Mvc;

using System.Data.Entity;

using System.Text;

namespace DemoGrids.BussinessService

{

public class BussinessServices

{

public variable GetCustomers(String Word, int Page, int rows, string searchString)

{

variable v = new variable();

List<CustomerViewModel> customermodel = new List<CustomerViewModel>();

using (DatabaseContext db = new DatabaseContext())

{

v.PageIndex = Convert.ToInt32(Page) - 1;

v.PageSize = rows;

customermodel = (from customer in db.Customers

select new CustomerViewModel

{

CustomerID = customer.CustomerID,

ContactName = customer.ContactName,

ContactTitle = customer.ContactTitle,

City = customer.City,

PostalCode = customer.PostalCode,

Country = customer.Country,

Phone = customer.Phone

}).ToList();

v.totalRecords = customermodel.Count();

v.totalPages = (int)Math.Ceiling((float)v.totalRecords / (float)rows);

if (v.sort.ToUpper() == v.DESC)   // getting error here 

// if (v.sort.ToUpper() == "DESC")

{

customermodel = customermodel.OrderByDescending(s => s.CustomerID).ToList();

customermodel = customermodel.Skip(v.PageIndex * v.PageSize).Take(v.PageSize).ToList();

}

else

{

customermodel = customermodel.OrderBy(s => s.CustomerID).ToList();

customermodel = customermodel.Skip(v.PageIndex * v.PageSize).Take(v.PageSize).ToList();

}

if (!string.IsNullOrEmpty(searchString))

{

customermodel = customermodel.Where(m => m.Country == searchString).ToList();

}

var jsonData = new

{

total = v.totalPages,

Page,

records = v.totalRecords,

rows = customermodel

};

return new variable {total=v.totalPages,PageIndex=v.PageIndex,records=v.records,customerModel= customermodel };

}

}

}

}