We have created our own data reference to connect to a webservice. This webservice can return value,NULL or an empty string (''). We have connect this data reference to an AF attribute of the type Double. When NULL is returned by the web service the value in AF Explorer for the attribute shows "Cannot set System.Double to a null value". When we changed the type of the attribute to a String then the value of the attribute shows a '-'. We want to display '-' when the type of AF attribute is Double and the value is NULL.
It look like that the conversion is done somewhere in AF and not in the Data reference itself. Is this possible by overriding a function or in a other way to get the behaviour we want?