Hi there.

This bulk update query throw an exception(null reference exception):

session.Query.All<AttachmentEntity>
.Where(a => a.Id.In(existingAttachments))
.Set(a => a.LastDate, dateNow)
.Update();

existingAttachments is IList<long>, dateNow is captured DateTime.Now

with .Where(a => a.Id == someId) works fine.

seems that extension method "In" could not be parsed in expression tree.