Linq to SQL DataContext fails to update Enum field in database for inherited objects

Question

I have MSSQL database with one table:

CREATE TABLE Hierarchy (
    Id      UNIQUEIDENTIFIER PRIMARY KEY,
    version TIMESTAMP NOT NULL,
    DiscKey INT NOT NULL,
    Enum    INT NOT NULL
);

I have objects hierarchy with one base class and two subclasses. I use attributes for mapping objects to database structure:

enum ObjectType { A = 1, B = 2 }
enum EnumA { Foo = 1, Bar = 2 }
enum EnumB { Xxx = 1, Yyy = 2 }

[Table(Name = "Hierarchy")]
[InheritanceMapping(Code = ObjectType.A, Type = typeof(DerivedA), IsDefault = true)]
[InheritanceMapping(Code = ObjectType.B, Type = typeof(DerivedB))]
class Base
{
    [DataMember, Column(Name = "Id", DbType = "UniqueIdentifier", CanBeNull = false, IsPrimaryKey = true)]
    public Guid Id;

    [Column(Name = "DiscKey", DbType = "int", CanBeNull = false, IsDiscriminator = true)]
    public ObjectType DiscKey;

    [Column(Name = "version", DbType = "RowVersion", CanBeNull = false, IsVersion = true, IsDbGenerated = true)]
    public byte[] Version { get; protected set; }
}

class DerivedA : Base
{
    [DataMember, Column(Name = "Enum", DbType = "int", CanBeNull = false)]
    public EnumA Enum;
}

class DerivedB : Base
{
    [DataMember, Column(Name = "Enum", DbType = "int", CanBeNull = false)]
    public EnumB Enum;
}

Note: I would like to store EnumA and EnumB fields in one column!

In two different units of work, I'm trying: to create object, and to update it afterwards:

var objId = Guid.NewGuid();
var o1 = new DerivedA {Id = objId, Enum = EnumA.Foo};
using (var context = new DataContext(connectionString))
{
    context.GetTable(typeof(Base)).InsertOnSubmit(o1);
    context.SubmitChanges();
}
var o2 = new DerivedA {Id = objId, Enum = EnumA.Bar};
using (var context = new DataContext(connectionString))
{
    context.GetTable(typeof(Base)).Attach(o2, true);
    context.SubmitChanges();
}

Problem: the second SubmitChanges() throws an exception:

Unhandled Exception: System.ArgumentException: The argument 'value' was the wrong type. Expected 'ConsoleApplication8.EnumA'. Actual 'ConsoleApplication8.EnumB'.
at System.Data.Linq.SqlClient.SqlBinder.Visitor.VisitAssign(SqlAssign sa)
at System.Data.Linq.SqlClient.SqlVisitor.Visit(SqlNode node)
at System.Data.Linq.SqlClient.SqlVisitor.VisitUpdate(SqlUpdate update)
at System.Data.Linq.SqlClient.SqlVisitor.Visit(SqlNode node)
at System.Data.Linq.SqlClient.SqlVisitor.VisitBlock(SqlBlock b)
at System.Data.Linq.SqlClient.SqlVisitor.Visit(SqlNode node)
at System.Data.Linq.SqlClient.SqlBinder.Visitor.VisitIncludeScope(SqlIncludeScope scope)
at System.Data.Linq.SqlClient.SqlVisitor.Visit(SqlNode node)
at System.Data.Linq.SqlClient.SqlBinder.Bind(SqlNode node)
at System.Data.Linq.SqlClient.SqlProvider.BuildQuery(ResultShape resultShape, Type resultType, SqlNode node, ReadOnlyCollection`1 parentParameters, SqlNodeAnnotations annotations)
at System.Data.Linq.SqlClient.SqlProvider.BuildQuery(Expression query, SqlNodeAnnotations annotations)
at System.Data.Linq.SqlClient.SqlProvider.System.Data.Linq.Provider.IProvider.Execute(Expression query)
at System.Data.Linq.ChangeDirector.StandardChangeDirector.DynamicUpdate(TrackedObject item)
at System.Data.Linq.ChangeDirector.StandardChangeDirector.Update(TrackedObject item)
at System.Data.Linq.ChangeProcessor.SubmitChanges(ConflictMode failureMode)
at System.Data.Linq.DataContext.SubmitChanges(ConflictMode failureMode)
at ConsoleApplication8.Program.Main()

But I do not use neither DerivedB, nor EnumB in my code.

Answer 1

Inherite both enum from int . Example;

enum EnumA : int { Foo = 1, Bar = 2 } enum EnumB : int { Xxx = 1, Yyy = 2