Compare of Nullable Chars fails in Where

[inosyryev]

LINQ

from current in repository.EngineeringCircuitEnds
from previous in repository.EngineeringCircuitEnds
where current.Gender == previous.Gender
select new { CurrentId = current.EngineeringCircuitID, PreviousId = previous.EngineeringCircuitID };

SQL

Can't generate

Problems

Exception:
System.InvalidCastException : Unable to cast object of type 'System.Linq.Expressions.PropertyExpression' to type 'System.Linq.Expressions.ConstantExpression'.

Workarounds

A workaround for problem is to handle null case manually:

from current in repository.EngineeringCircuitEnds
from previous in repository.EngineeringCircuitEnds
where (current.Gender ?? ' ') == (previous.Gender ?? ' ')
select new { CurrentId = current.EngineeringCircuitID, PreviousId = previous.EngineeringCircuitID };

Generated expression file

//---------------------------------------------------------------------------------------------------
// This code was generated by BLToolkit.
//---------------------------------------------------------------------------------------------------
using System;
using System.Linq.Expressions;

using NUnit.Framework;

namespace SPX.DEF.FromTo.UnitTest
{
    [System.Runtime.CompilerServices.CompilerGeneratedAttribute()]
    class <>c__DisplayClassf
    {
        public SPX.GCIS.Data.Sql.SqlServerDataRepository repository;
    }
}

namespace SPX.GCIS.Data.Sql
{
    [BLToolkit.DataAccess.TableNameAttribute(Name = "EngineeringCircuitEnd")]
    public class EngineeringCircuitEndRecord
    {
        [BLToolkit.DataAccess.PrimaryKeyAttribute((Int32)1)]
        [BLToolkit.DataAccess.IdentityAttribute()]
        public Int64 EngineeringCircuitID { get; set; }

        [BLToolkit.Mapping.NullableAttribute()]
        public Char? Gender { get; set; }
    }
}

namespace SPX.GCIS.Data.Sql
{
    public class SqlServerDataRepository : BLToolkit.Data.DbManager, System.ComponentModel.IComponent, IDisposable, BLToolkit.Data.Linq.IDataContext, BLToolkit.Mapping.IMappingSchemaProvider
    {
        public SqlServerDataRepository()
        {
            throw new NotImplementedException();
        }

        public SqlServerDataRepository(string connectionString)
        {
            throw new NotImplementedException();
        }

        public SqlServerDataRepository(System.Data.IDbConnection connection)
        {
            throw new NotImplementedException();
        }

        public BLToolkit.Data.Linq.Table<SPX.GCIS.Data.Sql.EngineeringCircuitEndRecord> EngineeringCircuitEnds { get; set; }
    }
}

namespace Data.Linq
{
    [TestFixture]
    public class UserTest : TestBase
    {
        [Test]
        public void Test()
        {
            // Table(EngineeringCircuitEndRecord).SelectMany(current => value(SPX.DEF.FromTo.UnitTest.BlToolkitTesting+<>c__DisplayClassf).repository.EngineeringCircuitEnds, (current, previous) => new <>f__AnonymousTypea`2(current = current, previous = previous)).Where(<>h__TransparentIdentifiere => (Convert(<>h__TransparentIdentifiere.current.Gender) == Convert(<>h__TransparentIdentifiere.previous.Gender))).Select(<>h__TransparentIdentifiere => new <>f__AnonymousTypeb`2(CurrentId = <>h__TransparentIdentifiere.current.EngineeringCircuitID, PreviousId = <>h__TransparentIdentifiere.previous.EngineeringCircuitID))
            ForEachProvider(db =>
                Table(EngineeringCircuitEndRecord)
                    .SelectMany(
                        (SPX.GCIS.Data.Sql.EngineeringCircuitEndRecord current) => value(SPX.DEF.FromTo.UnitTest.BlToolkitTesting+<>c__DisplayClassf).repository.EngineeringCircuitEnds,
                        (SPX.GCIS.Data.Sql.EngineeringCircuitEndRecord current, SPX.GCIS.Data.Sql.EngineeringCircuitEndRecord previous) => new
                        {
                            current = current,
                            previous = previous
                        })
                    .Where(
                        (tpe) => ((int?)tpe.current.Gender == (int?)tpe.previous.Gender))
                    .Select(
                        (tpe) => new
                        {
                            CurrentId = tpe.current.EngineeringCircuitID,
                            PreviousId = tpe.previous.EngineeringCircuitID
                        }));
        }
    }
}