“Invalid Index n for this SqlParameterCollection with Count=n” OR “foreign key cannot be null”

Question

I have been successfully using NHibernate for quite some time now and have been able to solve a lot of pitfalls with an application that I developed with it and that is ru

Answer 1

Aaargh! I was put so much on a wrong leg with this infamous “Invalid Index n for this SqlParameterCollection with Count=n” error that I overlooked the obvious: A duplicate mapping of a field for ONE of the classes. In that particular mapping I left this error, where the primary key is also defined as a property:

 <id name="ID" column="ID">
   <generator class="guid" />
 </id>
 <property name="ID" column="ID" /> 

Now that was a waste of time trying to debug that!