Question

I have a bigger code block which I have recreated in this simpler example:

    Dim evalcheck As Boolean
    Dim aEntityId, bEntityId As Integer?
    Dim aCheckNumber, bCheckNumber As Integer?

    aEntityId = Nothing
    bEntityId = Nothing
    aCheckNumber = Nothing
    bCheckNumber = Nothing
    evalcheck = aEntityId = bEntityId And aCheckNumber = bCheckNumber

I get nullable object must have a value when I compare Nothing to Nothing pairs.

Is there a quick fix for the eval part –

evalcheck = aEntityId = bEntityId And aCheckNumber = bCheckNumber

Answer 1

You should really use parentheses for readability. Even then, the comparison is ugly.

If ((aEntityId IsNot Nothing And bEntityId IsNot Nothing) AndAlso (aEntityId = bEntityId)) Or (aEntityId Is Nothing And bEntityId Is Nothing) Then
    If ((aCheckNumber IsNot Nothing And bCheckNumber IsNot Nothing) AndAlso (aEntityId = bEntityId)) Or (aCheckNumber Is Nothing And bCheckNumber Is Nothing) Then
        evalcheck = True
    Else
        evalcheck = False
    End If
Else
    evalcheck = False
End If

I prefer this method better though

Private Function NullableIntsEqual(ByVal a As Integer?, ByVal b As Integer?) As Boolean
    If ((a IsNot Nothing And b IsNot Nothing) AndAlso (a = b)) Or (a Is Nothing And b Is Nothing) Then
        Return True
    Else
        Return False
    End If
End Function

You evalcheck line becomes

evalcheck = NullableIntsEqual(aEntityId, bEntityId) And NullableIntsEqual(aCheckNumber, bCheckNumber)