xml in vb.net

redeye2 · October 21st, 2004, 02:29 AM

From the book "professional vb.net 2003" I am creating the code as per the instructions but get an error message:

"Object reference not set to an instance of an object"

The problem is highlighted where it is asterixed in the code below:

        prescriptions = serialize.Deserialize(dehydrated)

        Dim prescription As WXClientPrescription
        For Each prescription In prescriptions.prescriptions
            Console.Out.WriteLine("{0},{1},{2}", _
                    prescription.dentistName, _
                    prescription.medicationID, _
                    prescription.quantity)

        Next**

It is taken from chapter 10 p307.

jaucourt · November 10th, 2004, 06:48 PM

I don't think it will be throwing an exception where you have marked with an asterisk. Much more likely is the previous line where you are referring to three different properties of the prescription object. These three properties need to be checked for whether the property exists or not; something like

Code:

Dim dentistName as String, medicationID, quantity as Integer
If IsDbNull(prescription.dentistName) Then _
    dentistName = "" Else _
    dentistName = prescription.dentistName
If IsDbNull(medicationID) Then _
    medicationID = 0 Else _
    medicationID = prescription.medicationID
If IsDbNull(prescription.quantity) Then _
    quantity = 0 Else _
    quantity = prescription.quantity
Console.Out.WriteLine("{0},{1},{2}", _
                    dentistName, _
                    medicationID, _
                    quantity)