Question

I have a simple function which returns a single column’s data from a database based on an inline SQL statement like this (simplified version):

Function GetId(ByVal name As String) As Object

    Dim sql As String = "Select Id From table where username = '" & name & "'"

    Using cmd As New SqlCommand
        cmd.Connection = conn
        cmd.CommandType = CommandType.Text
        cmd.CommandText = sql
        GetId = cmd.ExecuteScalar
    End Using

End Function

If the SQL returns a row it can be NULL or integer, or alternatively SQL does not return anything.

In another part of the code I have:

Dim userId As Object = New Object

userId = GetBillingGroupToInvoice(name)

Is it OK to use Object as a return type here. If not what should I specify as a return type of this function? This is in VB but answers in C# is also OK.

Thanks

Answer 1

Your function should probably return a nullable integer, returning Nothing when your SQL server returns nothing or DBNull (if you don’t want to make a difference between No rows returned and DBNull).

Function GetId(ByVal name As String) As Integer?

    Dim sql As String = "Select Id From table where username = '" & name & "'"

    Using cmd As New SqlCommand
        cmd.Connection = conn
        cmd.CommandType = CommandType.Text
        cmd.CommandText = sql
        Dim result = cmd.ExecuteScalar
        Return If(DBNull.Value.Equals(result), 
                  Nothing, 
                  DirectCast(result, Integer?))
    End Using

End Function

---

Then, you would call your method like this:

Dim userId = GetBillingGroupToInvoice(name)
If userId.HasValue Then
    'Do something with userId.Value'
End If