Using TFS API, how can I find the comments which were made on a Code Review?

We have a new requirement to pull code review comments from TFS and here is a short example of what we implemented. The workItemId has to be queried through another method. You can even look it up in Visual Studio or through a TFS query in the UI. This is a small subset of what is available and what we are using. I found this link to be helpful after digging through MSDN.

 public List<CodeReviewComment> GetCodeReviewComments(int workItemId)
 {
        List<CodeReviewComment> comments = new List<CodeReviewComment>();

        Uri uri = new Uri(URL_TO_TFS_COLLECTION);
        TeamFoundationDiscussionService service = new TeamFoundationDiscussionService();
        service.Initialize(new Microsoft.TeamFoundation.Client.TfsTeamProjectCollection(uri));
        IDiscussionManager discussionManager = service.CreateDiscussionManager();

        IAsyncResult result = discussionManager.BeginQueryByCodeReviewRequest(workItemId, QueryStoreOptions.ServerAndLocal, new AsyncCallback(CallCompletedCallback), null);
        var output = discussionManager.EndQueryByCodeReviewRequest(result);

        foreach (DiscussionThread thread in output)
        {
            if (thread.RootComment != null)
            {
                CodeReviewComment comment = new CodeReviewComment();
                comment.Author = thread.RootComment.Author.DisplayName;
                comment.Comment = thread.RootComment.Content;
                comment.PublishDate = thread.RootComment.PublishedDate.ToShortDateString();
                comment.ItemName = thread.ItemPath;
                comments.Add(comment);
            }
        }

        return comments;
    }

    static void CallCompletedCallback(IAsyncResult result)
    {
        // Handle error conditions here
    }

    public class CodeReviewComment
    {
        public string Author { get; set; }
        public string Comment { get; set; }
        public string PublishDate { get; set; }
        public string ItemName { get; set; }
    }

I don't have code examples, but according to this discussion, you should be able to get to code review comments with functionality in the Microsoft.TeamFoundation.Discussion.Client namespace.

Specifically the comments are accessible via the DiscussionThread class. And you should be able to query discussions using IDiscussionManager.