Question

I have two Sql Server tables accessed through Entity Framework 4. They are joined by a single key with 0 to 1 rows on the dependent side of the join. Here is my linq query.

     var typeDtoList = from type in typeList
                       select (new DxStudioTypeDto(parent, 
                                                   isChildrenLoadOnDemand,
                                                   businessFacade,
                                                   server,
                                                   database,
                                                   type.typeGuid,
                                                   type.typeName,
                                                   type.writerName,
                                                   type.managerName,
                                                   type.Reporting_Type.MRef_Status,
                                                   type.Reporting_Type.Exists_In_Drop));

Obviously, if the Reporting_Type returns zero rows, the linq expression throws a null reference exception on the last two parameters of the DxStudioTypeDto constructor:

type.Reporting_Type.MRef_Status,
type.Reporting_Type.Exists_In_Drop));

Is there a way to detect the absence of a Reporting_Type row and substitute a default string? DxStudioTypeDto is an immutable type, so I need all the parameters available when I instanciate a new object. Any other strategies for this situation?

Answer 1

Did you try this?

((type.Reporting_Type == null) ? "some default value" : type.Reporting_Type.MRef_Status)

I know sometimes the EF engine returns a “the provider does not support this operation” for this kind of thing, but it’s worth a try.