Update BP,Item error

Question

When I try to update a BusinessPartner or an Item I get the errormessage:
-1107 - The object's key is not set
This is what I do (I use VB.NET):
First I create an xml file of the bp and then:
Dim oDestBP As SAPbobsCOM.BusinessPartners = oCompany2.GetBusinessObjectFromXML(sFileName, 0)
oDestBP.Add()
oCompany2.GetLastError(oErr, oErrmsg)
Select Case oErr
    Case 0                    'Everything went OK
         Exit Select
    Case -1                   'BP already exists
          oDestBP.Update()
end select
The adding is no problem if the bp doesn't exists but the updating goes wrong.
Can somebody help me?
Thx

Answer 1

When you make
odestbp.getbykey(bpcode)
you are removing all information odestbp had before and charging the bp information you have in your current company.
You need to have 2 bp instances. One that reads from the xml file the information and another one that reads from the database (using GetByKey). Then you must copy one by one the parameters you want to update from the xml instance to the getbykey instance.
I don't know a method that allows to copy the objects directly. The only way it could work is when the bp doesn't exist in the second company, then you can read from the xml and create directly in the second company.
Hope it helps
Trinidad.