LINQ to CSLA bug..??

chachek posted on Friday, May 22, 2009

In CSLA 3.6.3, when trying to execute:

DateTime? maxLastUpdated = myBusinessList.Max(x => x.LastUpdated);

I get the following ArgumentException:

Object of type 'System.Func`2[My.Entities.BusinessEntity,System.Nullable`1[System.DateTime]]' cannot be converted to type 'System.Func`2[My.Entities.BusinessEntity,System.Nullable`1[System.Int32]]'.

It seems that the CslaQueryProvider is trying to use a different overload of the Max method.

It works when I cast myBusinessList to IEnumerable<BusinessEntity>

AaronErickson replied on Friday, May 22, 2009

Can you provide your implementation of myBusinessList? I just built a test that exercises Max with a similar lambda and was not able to repro this. I used a datetime for my prop, casted it to a DateTime?, and it worked. Here is my code:

CollectionExtendingIQueryable random = new CollectionExtendingIQueryable();

random.Add(new RandomThing(1));
random.Add(new RandomThing(2));
random.Add(new RandomThing(3));
random.Add(new RandomThing(4));
random.Add(new RandomThing(5));

var a = from r in random where r.SomeVal >= 0 select r;
Assert.IsTrue(a.Max(r => r.SomeDateTime) == new DateTime(5));
//did this last one to make sure the nullable isnt causing this issue
DateTime? maxDateTime = random.Max(r => r.SomeDateTime);

RockfordLhotka replied on Friday, May 22, 2009

This fails Aaron - though if you change the property type to DateTime instead of DateTime? it works, so it must have to do with Nullable<T>:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Csla;

namespace ConsoleApplication1
{
class Program
{
    static void Main(string[] args)
    {
      var list = new MyList();
      list.Add(new MyChild { Id = 5, ADate = DateTime.Parse("3/1/02") });
      list.Add(new MyChild { Id = 15, ADate = DateTime.Parse("4/1/01") });
      list.Add(new MyChild { Id = 2, ADate = DateTime.Parse("5/1/02") });
      list.Add(new MyChild { Id = 25, ADate = DateTime.Parse("3/1/03") });
      list.Add(new MyChild { Id = 1, ADate = DateTime.Parse("8/1/02") });

      var max = list.Max(c => c.Id);
      Console.WriteLine(max);
      DateTime? maxDate = list.Max(c => c.ADate);
      Console.WriteLine(maxDate);
      Console.ReadLine();
    }
}

[Serializable]
public class MyList : Csla.BusinessListBase<MyList, MyChild>
{
}

[Serializable]
public class MyChild : Csla.BusinessBase<MyChild>
{
    private static PropertyInfo<int> IdProperty = RegisterProperty<int>(c => c.Id);
    public int Id
    {
      get { return GetProperty(IdProperty); }
      set { SetProperty(IdProperty, value); }
    }

    private static PropertyInfo<DateTime?> ADateProperty = RegisterProperty<DateTime?>(c => c.ADate);
    public DateTime? ADate
    {
      get { return GetProperty(ADateProperty); }
      set { SetProperty(ADateProperty, value); }
    }
}
}