How to solve "Batch update returned unexpected row count from update; actual row count: 0; expected: 1" problem?
The error means that the SQL INSERT statement is being executed, but the ROWCOUNT being returned by SQL Server after it runs is 0, not 1 as expected.
There are several causes, from incorrect mappings, to UPDATE/INSERT triggers that have rowcount turned off.
Your best beat is to profile the SQL statements and see what happens. To do that either turn on nHibernate sql logging, or use the sql profiler. Once you have the SQL you may know the cause, if not try running the SQL manually and see what happens.
Also I suggest you to post your mapping, as it will help people spot any issues.
This can happen when trigger(s) execute additional DML (data modification) queries which affect the row counts. My solution was to add the following at the top of my trigger:
SET NOCOUNT ON;
This may occur because of Auto increment primary key. To solve this problem do not inset auto increment value with data set. Insert data without the primary key.