Missing nodes from a webservice.

InfoPath is very particular about the type of document it processes - this due to its very stringent implementation of XSD Schemas. InfoPath will complain immediately if it encounters nodes that do not fit the schema design (nodes not defined in schema, nodes out of position, multiple nodes where not defined as repeating)

If a node is missing from the instance document and the schema dictates the optional presence of this node, InfoPath will accept the document as valid. However, if there are any controls being bound to the missing field, InfoPath will disable the field in the UI, as nothing can be written to a missing node.

This became painfully apparent in our early iterations of our InfoPath form. We noticed several fields being locked out in the form only to discover the fields were missing from the XML documents returned by our Webservice. We tracked this down to the Enterprise Library's Database Datatable to XML conversion.

Any null values in a recordset are not converted to empty fields in the resulting XML, but rather they are just omitted. Our solution was to use the schema to build ourselves an empty instance document and populate it with the data from the recordset. This way we are guaranteed to get all required nodes returned from a webservice

Since a schema document is simply another XML document, parse the XSD document and programmatically build the instance document starting from the root node element definition.. TBC