Public Class SqlDatabase
    ' ...
 
    Public Function Query(ByVal Cmd As String) As SqlDataReader
    ' ...
    Return ThisReader
    End Function
End Class

Module SqlExtensions
    <Extension()> _
    Public Function QueryToXml(ByVal Obj As SqlDatabase, ByVal Cmd As String) _
    As String
        Using Reader As SqlDataReader = Query(Cmd)
            Dim Builder As StringBuilder = New StringBuilder
 
            Using Writer As XmlWriter = XmlWriter.Create(Builder)
                ' Reader auslesen und in Writer schreiben
            End Using
 
            Return Builder.ToString
        End Using
    End Function
 
    <Extension()> _
    Public Function QueryToByte(ByVal Obj As SqlDatabase, ByVal Cmd As String) _
    As Byte()
        Using Reader As SqlDataReader = Query(Cmd)
            Dim Bytes() As Byte()
 
            ' Reader auslesen und in Byte-Array schreiben
 
            Return Bytes
        End Using
    End Function
End Module