Invalid index 1 for this SqlParameterCollection with Count=1
If you ever get this error it could be because your property mappings are mapped to the same column.
<property name="FirstName" column="FirstName" type="string" not-null="true" /> <property name="LastName" column="FirstName" type="string" not-null="true" />
This will cause this error, the fix is to map your properties correctly.
<property name="FirstName" column="FirstName" type="string" not-null="true" /> <property name="LastName" column="LastName" type="string" not-null="true" />