Was this resolved at all? I have a similar issue:
Steps to Reproduce
1) I have a DB table with a column which is varchar(1024)
2) I want this column to only contain unique strings
3) So I add a trigger to the column to check for the data entered and use RaisError if any problems
4) I setup my Datagrid/ObjectDataSource/BLL/DAL and all works fine in aspx, the page errors with the correct message.
5) I add in an AJAX Update Panel and *it* (the ASP.NET AJAX Libraries) just spits out a JSON string containing an alert message "An exception occured by the the target of an invocation". THAT is not the correct error string.
Why is it not? and how do I alter this behaviour to make it send a JSON string containing the correct Error message?
Thank