ToDataSourceResult Problems with NHibernate in a Grid

[Frank]

Hello,

I am having trouble using the ToDataSourceResult method in combination with NHibernate.

Here is a minimal example of what I'm doing:

            using ( var session = NHibernate.DefaultFactory.OpenStatelessSession())
            {
                IQueryable<MyDataRow> myQuery = session.Query<MyDataRow>();
                DataSourceResult myResult = dataRowRepo.ToDataSourceResult(request, x => new ListRowViewModel()
                {
                    ID = x.ID,
                    Property2 = x.Property2
                });
                return Json(myResult, JsonRequestBehavior.AllowGet);
            }

This works perfectly fine as long as I don't try to use aggregate or grouping. As soon as I start that my service returns something like this:

Specified method is not supported.

Or for aggregation:
Query Source could not be identified: ItemName = x,
ItemType = MyDataRow, Expression
= from MyDataRow x in
value(NHibernate.Linq.NhQueryable`1[MyDataRow])

And help or suggestions would be greatly appreciated.

[Atanas Korchev]

Hi Frank,

It seems that the NHibernate Linq provider can't interpret some of the LINQ expression trees that ToDataSourceResult generates. In such cases we can suggest only two things - implement custom binding thus eliminating the ToDataSourceResult call or try to perform the problematic operations (e.g. grouping) in memory. Here is how to do that:

        public ActionResult Customers_Read([DataSourceRequest]DataSourceRequest request)
        {
            var customers = GetCustomers();

            var grouping = request.Groups;

            //Clear the grouping options
            request.Groups = null;

            //Execute the query without grouping
            var result = customers.ToDataSourceResult(request);

            //Restore grouping
            request.Groups = grouping;

            //Call ToDataSourceResult to do the grouping in memory
            result = result.Data.ToDataSourceResult(request);

            return Json(result);
        }

Regards,
Atanas Korchev
Telerik

[Mike]

Hello,

I'm using the latest version of Kendo UI, and still have the same problem as you Frank.
Is there any news about this subject ? 

Thanks for help
Regards

[Atanas Korchev]

Hi,

The code which handles grouping hasn't been changed. Perhaps the NHibernate Linq support has been improved. If this is still a problem with the latest version of NHibernate you can try the workarounds suggested in my previous reply.

Regards,
Atanas Korchev
Telerik

 

 

[lee hom]

Hello,

      Have you solve the grouping problem of NHibernate 4.0 except twice ToDataSourceResult?   I have the same problem too.

 

Thanks for help
Regards

[lee hom]

Hi,

    NHibernate support GroupBy Linq method, but when we use ToDataSourceResult with grouping, it still has some exception, can you fix it?

    Now I can use ToDataSourceResult like this:

public static DataSourceResult ToGroupingDataSourceResult<TModel, TResult>(this IQueryable<TModel> enumerable, DataSourceRequest request, Func<TModel, TResult> selector)
{
    var grouping = request.Groups;
    var hasGrouping = grouping != null && grouping.Count > 0;
    if (!hasGrouping)
    {
        return enumerable.ToDataSourceResult(request, selector);
    }
    //Clear the grouping options
    request.Groups = null;

    //Execute the query without grouping
    var result = enumerable
        .ToDataSourceResult(request, selector)
        ;

    //Restore grouping
    request.Groups = grouping;

    //Call GroupBy to do the grouping in memory
    result.Data = result.Data.AsQueryable().GroupBy(grouping);
    return result;
}

Regards,

Thanks