Question

I am following Phil Haacks tutorial on using JQGrid with ASP.Net MVC. My application is ASP.Net MVC 3 using Entity Framework 4.

I have the following code to perform the sorting and paging for my data which is returned to the JQGrid

var query = equipService.GetAllEquipment().AsQueryable()
                .OrderBy("it." + sidx + " " + sord)
                .Skip(pageIndex * pageSize)
                .Take(pageSize);

However, this code creates an error at the .OrderBy(“it.” + sidx + ” ” + sord) line. The error is

System.Linq.Queryable.OrderBy<TSource,TKey>(System.Linq.IQueryable<TSource>, System.Linq.Expressions.Expression<System.Func<TSource,TKey>>)' cannot be inferred from the usage. Try specifying the type arguments explicitly.

The query is calling a method, GetAllEquipment(), in my service layer which looks like this

public List<Equipment> GetAllEquipment()
    {
        List<Equipment> equipList = new List<Equipment>();
        equipList = equipRepository.GetAllEquipment();

        return equipList;
    }

This method, then calls the same name of method in my repository, like so

public List<Equipment> GetAllEquipment()
    {
        var query = (from e in Data.DBEntities.Equipments
                     select e).ToList();

        return query;
    }

I can kind of solve the problem by creating an instance of my objectcontext in my controller method and use this code

using (AssetEntities context = new AssetEntities())
        {
            int pageIndex = Convert.ToInt32(page) - 1;
            int pageSize = rows;
            int totalRecords = context.Equipments.Count();
            int totalPages = (int)Math.Ceiling((float)totalRecords / (float)pageSize);


            var query = context.Equipments
              .OrderBy("it." + sidx + " " + sord)
              .Skip(pageIndex * pageSize)
              .Take(pageSize);

        }

However, I don’t really want to do this, rather I would like to keep to the repository pattern I use throughout my application for all database interaction.

Any ideas on how I can fix this?

Thanks as ever everyone.

Answer 1

I recommed you to use PropertyInfo, GetProperty or FieldInfo, GetField depend on your data model. In the case you can implement OrderBy operation without any extensions. See the answer for details.

UPDATED: I reread your question carefully one more time. It seems to me, that your problem is inside of GetAllEquipment method. It returns List<Equipment> and not IQueryable<Equipment>. So the GetAllEquipment method get “SELECT * FROM it.Equipment” and return the data as a List which are no more Entity. With equipService.GetAllEquipment().AsQueryable() you will have IQueryable<Equipment> object, but you will not more use LINQ to Entity and so you should not use “it.” prefix before the names.