Commented Issue: EF4.3.1 on .NET 4 / VS2012 - The mapping of CLR type to EDM type is ambiguous because multiple CLR types match the EDM type [596]

We're using EF 4.3.1 code-first under .NET 4.0 and VS2012. We have a query that looks similar to the following:<br /><br />ctx.Set<Entities.A>().Select(a => new DTO.A { Id = a.Id, Name = a.Name }).ToArray();<br /><br />Entities.A is defined in an assembly called Entities and DTO.A is defined in an assembly called DTO. Under VS2010 EF 4.3 this worked fine, but under EF 5.0 it throws the following exception:<br /><br />Schema specified is not valid. Errors: <br />The mapping of CLR type to EDM type is ambiguous because multiple CLR types match the EDM type 'A'. Previously found CLR type 'Entities.A', newly found CLR type 'DTO.A'.<br /><br />Stack trace is<br /><br />at System.Data.Metadata.Edm.ObjectItemCollection.LoadAssemblyFromCache(ObjectItemCollection objectItemCollection, Assembly assembly, Boolean loadReferencedAssemblies, EdmItemCollection edmItemCollection, Action'1 logLoadMessage)<br />at System.Data.Metadata.Edm.ObjectItemCollection.ImplicitLoadAssemblyForType(Type type, EdmItemCollection edmItemCollection)<br />at System.Data.Metadata.Edm.MetadataWorkspace.ImplicitLoadAssemblyForType(Type type, Assembly callingAssembly)<br />at System.Data.Objects.ELinq.ExpressionConverter.TryGetValueLayerType(Type linqType, TypeUsage& type)<br />at System.Data.Objects.ELinq.ExpressionConverter.GetCastTargetType(TypeUsage fromType, Type toClrType, Type fromClrType, Boolean preserveCastForDateTime)<br />at System.Data.Objects.ELinq.ExpressionConverter.CreateCastExpression(DbExpression source, Type toClrType, Type fromClrType)<br />at System.Data.Objects.ELinq.ExpressionConverter.ConvertTranslator.TranslateUnary(ExpressionConverter parent, UnaryExpression unary, DbExpression operand)<br />at System.Data.Objects.ELinq.ExpressionConverter.UnaryTranslator.TypedTranslate(ExpressionConverter parent, UnaryExpression linq)<br />at System.Data.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)<br />at System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)<br />at System.Data.Objects.ELinq.ExpressionConverter.UnaryTranslator.TypedTranslate(ExpressionConverter parent, UnaryExpression linq)<br />at System.Data.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)<br />at System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)<br />at System.Data.Objects.ELinq.ExpressionConverter.MemberInitTranslator.TypedTranslate(ExpressionConverter parent, MemberInitExpression linq)<br />at System.Data.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)<br />at System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)<br />at System.Data.Objects.ELinq.ExpressionConverter.TranslateLambda(LambdaExpression lambda, DbExpression input)<br />at System.Data.Objects.ELinq.ExpressionConverter.TranslateLambda(LambdaExpression lambda, DbExpression input, DbExpressionBinding& binding)<br />at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.OneLambdaTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, DbExpression& source, DbExpressionBinding& sourceBinding, DbExpression& lambda)<br />at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SelectTranslator.Translate(ExpressionConverter parent, MethodCallExpression call)<br />at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, SequenceMethod sequenceMethod)<br />at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq)<br />at System.Data.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)<br />at System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)<br />at System.Data.Objects.ELinq.ExpressionConverter.MemberInitTranslator.TypedTranslate(ExpressionConverter parent, MemberInitExpression linq)<br />at System.Data.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)<br />at System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)<br />at System.Data.Objects.ELinq.ExpressionConverter.TranslateLambda(LambdaExpression lambda, DbExpression input)<br />at System.Data.Objects.ELinq.ExpressionConverter.TranslateLambda(LambdaExpression lambda, DbExpression input, DbExpressionBinding& binding)<br />at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.OneLambdaTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, DbExpression& source, DbExpressionBinding& sourceBinding, DbExpression& lambda)<br />at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SelectTranslator.Translate(ExpressionConverter parent, MethodCallExpression call)<br />at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, SequenceMethod sequenceMethod)<br />at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq)<br />at System.Data.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)<br />at System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)<br />at System.Data.Objects.ELinq.ExpressionConverter.TranslateSet(Expression linq)<br />at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.UnarySequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call)<br />at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, SequenceMethod sequenceMethod)<br />at System.Data.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq)<br />at System.Data.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)<br />at System.Data.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)<br />at System.Data.Objects.ELinq.ExpressionConverter.Convert()<br />at System.Data.Objects.ELinq.ELinqQueryState.GetExecutionPlan(Nullable`1 forMergeOption)<br />at System.Data.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption)<br /><br />I'd understand the problem if the types were in the same assembly (a long documented issue with EF whereby it cannot disambiguate using just the entity name), but from a different assembly?<br /><br />Is this a regression, it used to work...?
Comments: It looks to me that the enum type lives in a separate assembly and the cast triggers loading types from this assembly. This assembly happen to contain the type 'DTO.A' which matches the 'Entities.A' type. This cause the ambiguity which in turn causes an exception to be thrown. Note that did not happen in .NET Framework 4 since enum types in EF4 were not supported and cast operation would not cause loading types from the other assembly so this is a regression in .NET Framework 4.5. EF6 is kind of not affected by this - the behavior will be the same regardless whether .NET Framework 4 or .NET Framework 4.5 is used - we will throw. Resetting release.