Get Child Count in Parent List SharePoint Lookup Field

I came across a requirement where I required the number of comments

 against a post in a child list (lstComments) maintained in the Parent list (lstPost).

Below is a very efficient way to achieve this

 using (SPSite site = new SPSite(webUrl))

            {

                using (SPWeb web = site.OpenWeb())

                {

                    SPList lstPost = web.Lists.TryGetList("Post");

                    SPList lstComments = web.Lists.TryGetList("Comments");

                    if (lstPost != null &&  lstComments != null )

                    {

                        SPField id= lstPost .Fields.TryGetFieldByStaticName("ID");

                        if (null != id)

                        {

                            // Create a PostID lookup field on the lstComments list.  

                            string PostIdName = lstComments .Fields.AddLookup("PostID", lstPost .ID, true);

                            SPFieldLookup PostIdField =

                                (SPFieldLookup)lstComments .Fields.GetFieldByInternalName(PostIdName );

                            PostIdField .LookupField = id.InternalName;

                            PostIdField .Update();

                            AddToDefaultView(lstComments , PostIdName );

                            // Create a CommentCount Lookup field to maintain child count in the lstPost list

                            string commentCountName = lstPost .Fields.AddLookup("CommentsCount", lstComments .ID, false);

                            SPFieldLookup commentCountField =

                                (SPFieldLookup)lstPost .Fields.GetFieldByInternalName(commentCountName );

                            commentCountField .LookupField = id.InternalName;

                            commentCountField .CountRelated = true;

                            commentCountField .Update();

                            AddToDefaultView(lstPost , commentCountName );

                        }

                    }

                }

            }