Returns the number of column properties that this ProDataObject represents.

A ProDataObject holds its data as a property list—one property per column. However, a ProDataObject might contain extra properties (reference properties) if it is involved in a data-relation (ProDataRelatonMetaData). This method returns the number of properties that map to a column. You can access these properties in sequence using the various ProDataObject set and get methods with the 0-based propertyIndex value up to the limit specified by this method.