[Solved] Problem with CustomBinding (DbIsNullExpression)

[Stefan]

Hello,
I'm having a problem during Filtering with CustomBinding enabled. It keeps throwing exceptions in my face. For brevities sake I attached a sample project. I sincerely hope I'm just doing something wrong, but I can't figure out what.

Also I think this problem is loosely related to http://www.telerik.com/community/forums/aspnet-mvc/grid/the-argument-to-dbisnullexpression-must-refer-to-a-primitive-or-reference-type.aspx

Thanks in advance,
Stefan

[Rosen]

Hello Stefan,

Looking at the code you have attached, it seems that a projection is made before the filtering which actually triggers the error. Therefore, changing  the code similar to the following should correct the issue:

public IEnumerable<InventoryItemViewModel> FindByCommand(GridCommand command)
{
    var data = _context.InventoryItems.AsQueryable();

    if (command.FilterDescriptors.Any())
        data = data.Where(ExpressionBuilder.Expression<InventoryItem>(command.FilterDescriptors));

    return data.Select(x => new InventoryItemViewModel
    {
        Id = x.Id,
        Name = x.Name
    });
}

If you would like to keep the projection before the filtering expression is added, the query should be executed after the projection

All the best,
Rosen
the Telerik team

[Stefan]

Guess that means meddling around with the FilterDescriptors where the names of the Model and ViewModel don't line up, right? 
For example I have property ArticleName on the ViewModel and Article.Name on the Model, which will probably choke the ExpressionBuilder.

If so, that sounds more like a workaround then a solution, but that's probably good enough for now.

[Luis]

I published a project that can help you in this situation.
You can find it on Codeplex and Nuget, please take a look.

http://tgh.codeplex.com/ 

https://nuget.org/packages/TelerikMvcGridCustomBindingHelper