LINQ - How to modify the select depending on value that DB would return

Question

I'm relatively new to Linq and I'm developing with .NET a function that instantiates a POCO with the selected fields of the linq query.

The problem is that one of these fields must be transformed "at runtime".

This is my malfunctioning example:

Private Shared Function GetInfectionHistory(HiveId As Long) As IList(Of HiveInfectionDetail)
    Using DB As LandDataModelUnitOfWork = Context.CreateUnitOfWork
            Dim historyResult = From I In DB.HiveAfbInfections
                                Where I.HiveId = HiveId
                                Select New HiveInfectionDetail With {
                                    .DateInfected = I.DateInfected,
                                    .DateCleaned = I.DateCleared,
                                    .PotentialAfbInfection = I.PotentialInfection,
                                    .AfbInfection = Not I.PotentialInfection
                                }
            If IsListEmpty(historyResult.ToList()) Then
                Return Nothing
            End If
            Return historyResult.ToList()
        End Using
End Function

and

Private Shared Function IsListEmpty(Of T)(source As IEnumerable(Of T)) As Boolean
        If source Is Nothing Then
            Return True
        End If
        Return Not source.Any()
    End Function
enter code here

The problematic line is when I assign a value to the property AfbInfection. This property will be the opposite value to the PotentialInfection in database. So if the I.PotentialInfection is True, then my property AfbInfection should be False. Doing it as above will cause an IndexOutOfRangeException - Index was outside the bounds of the array not sure what LinQ is doing with that NOT expression, but certainly it's not what I wish.

Is there any way to modify the DB field value when storing it into my custom object?

Thank you!

Answer 1

Try this:

Private Shared Function GetInfectionHistory(HiveId As Long) As IList(Of HiveInfectionDetail)
    Using DB As LandDataModelUnitOfWork = Context.CreateUnitOfWork
            Dim historyQuery1 = From I In DB.HiveAfbInfections
                                Where I.HiveId = HiveId
                                Select New With {
                                    .DateInfected = I.DateInfected,
                                    .DateCleaned = I.DateCleared,
                                    .PotentialInfection = I.PotentialInfection
                                }
            Dim historyQuery2 = From I In historyQuery1.ToArray()
                                Select New HiveInfectionDetail With {
                                    .DateInfected = I.DateInfected,
                                    .DateCleaned = I.DateCleaned,
                                    .PotentialAfbInfection = I.PotentialInfection,
                                    .AfbInfection = Not I.PotentialInfection
                                }
            Dim historyResult = historyQuery2.ToList()
            If IsListEmpty(historyResult) Then
                Return Nothing
            End If
            Return historyResult
        End Using
End Function