private static int GetWatermark(this ICommentDiscussionHeader discussion, int userId)
{
var comments = discussion.Comments.Where(c => c.AuthorUserId == userId).Select(c => c.Id);
var watermarks = discussion.Watermarks.Where(wm => wm.UserId == userId).Select(c => c.CommentId);
return(comments.Union(watermarks).Union(0).Max());
}
public static int GetUnreadCount(this ICommentDiscussionHeader commentDiscussion, int currentUserId)
{
var watermark = commentDiscussion.GetWatermark(currentUserId);
return(commentDiscussion.Comments.Where(c => c.IsVisibleTo(currentUserId)).Count(comment => watermark < comment.Id));
}