使用C＃中的嵌套回复对评论进行排序

Question

How do I sort my comments with nested replies? My data looks like:

var comments = new List<Comment>();
comments.Add(AddNewComment(1, null, ""));
comments.Add(AddNewComment(2, null, ""));
comments.Add(AddNewComment(3, null, ""));
comments.Add(AddNewComment(4, 1, ""));
comments.Add(AddNewComment(5, 4, ""));
comments.Add(AddNewComment(6, 1, ""));
comments.Add(AddNewComment(7, null, ""));
comments.Add(AddNewComment(8, 7, ""));
comments.Add(AddNewComment(9, 8, ""));
comments.Add(AddNewComment(10, 9, ""));
comments.Add(AddNewComment(11, 2, ""));
comments.Add(AddNewComment(12, 11, ""));
comments.Add(AddNewComment(13, 1, ""));
comments.Add(AddNewComment(14, 13, ""));

public Comment AddNewComment(int id, int? replyId, string body)
{
    return new Comment
    {
        Id = id,
        ReplyId = replyId,
        Body = body
    };
}

public class Comment
{
    public int Id { get; set; }
    public int Depth { get; set; }
    public string Body { get; set; }
    public int? ReplyId { get; set; }
}

I want to get something like:

/* 
 * 1        =>Depth:0
 * -4       =>Depth:1
 * --5      =>Depth:2
 * -13      =>Depth:1
 * --14     =>Depth:2
 * -6       =>Depth:1
 * 2        =>Depth:0
 * -11      =>Depth:1
 * --12     =>Depth:2
 * 3        =>Depth:0
 * 7        =>Depth:0
 * -8       =>Depth:1
 * --9      =>Depth:2
 * ---10    =>Depth:3
 * */

How can I do this?

Answer 1

To do this you will need to create a hierarchical sorting algorithm. Now the real question is do you want it to print that or be contained in another collection that is sorted in that fashion.

First I modified the comment collection to contain child Comment items in the Children property.

public class Comment
{
    /// <summary>
    /// gets the child comments
    /// </summary>
    public IList<Comment> Children { get; } = new List<Comment>();

    public int Id { get; set; }
    public int Depth { get; set; }
    public string Body { get; set; }
    public int? ReplyId { get; set; }
}

Now using the same code as you I have created a simple enumerator system which works out the children for the current comment. This is based on where ReplyId has a value and ReplyId == Id for the parent. ie. Id:4 Maps as a child to Id:1

public static void EnumerateTree(Comment comment, int depth, IEnumerable<Comment> collection)
{
    comment.Depth = depth;
    foreach(var child in collection.Where(c => c.ReplyId.HasValue && c.ReplyId == comment.Id))
    {
        comment.Children.Add(child);
        EnumerateTree(child, depth + 1, collection);
    }
}

So this is pretty basic, takes a comment which is the parent comment. A depth which is a 0 based index of the current depth. And finally the collection of comments. This works by first setting the depth to the comment. It then locates all the children in the collection that map to the comment (parent). Next iterates all of these comments adding them to the parent Children property and then recalls the EnumerateTree method for the child.

Finally we place this in your main class (under all your add comment stuff).

var sorted = new List<Comment>();
foreach(var comment in comments.Where(x => x.ReplyId == null)) //root comments do not have a reply id
{
    sorted.Add(comment);
    EnumerateTree(comment, 0, comments);
}

In the end you will have a hierarchical based view of the data.

Answer 2

You need a recursive algorithm. Try code below :

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Comment comment = new Comment();
            comment.Initialize();
            comment.SortComments();
            comment.PrintSortedComments();
        }
    }


    public class Comment
    {
        public static List<Comment> comments = new List<Comment>();
        public List<Comment> sortedComments = null;

        public int Id { get; set; }
        public int Depth { get; set; }
        public string Body { get; set; }
        public int? ReplyId { get; set; }

        public void Initialize()
        {
            comments.Add(AddNewComment(1, null, ""));
            comments.Add(AddNewComment(2, null, ""));
            comments.Add(AddNewComment(3, null, ""));
            comments.Add(AddNewComment(4, 1, ""));
            comments.Add(AddNewComment(5, 4, ""));
            comments.Add(AddNewComment(6, 1, ""));
            comments.Add(AddNewComment(7, null, ""));
            comments.Add(AddNewComment(8, 7, ""));
            comments.Add(AddNewComment(9, 8, ""));
            comments.Add(AddNewComment(10, 9, ""));
            comments.Add(AddNewComment(11, 2, ""));
            comments.Add(AddNewComment(12, 11, ""));
            comments.Add(AddNewComment(13, 1, ""));
            comments.Add(AddNewComment(14, 13, ""));
        }

        public Comment AddNewComment(int id, int? replyId, string body)
        {
            return new Comment
            {
                Id = id,
                ReplyId = replyId,
                Body = body
            };
        }
        public void SortComments()
        {
            sortedComments = new List<Comment>();

            List<Comment> levelZeroComments = comments.Where(x => x.ReplyId == null).OrderBy(x => x.Id).ToList();
            foreach (Comment comment in levelZeroComments)
            {
                sortedComments.Add(comment);
                comment.Depth = 0;
                RecusiveSort(comment.Id, 1);
            }
        }
        public void RecusiveSort(int id, int depth)
        {
            List<Comment> childComments = comments.Where(x => x.ReplyId == id).OrderBy(x => x.Id).ToList();

            foreach (Comment comment in childComments)
            {
                sortedComments.Add(comment);
                comment.Depth = depth;
                RecusiveSort(comment.Id, depth + 1);
            }

        }
        public void PrintSortedComments()
        {
            Console.WriteLine("/*");

            foreach (Comment sortComment in sortedComments)
            {
                Console.WriteLine(" * {0}{1}", new string('-', sortComment.Depth), sortComment.Id);
            }

            Console.WriteLine("* */");
            Console.ReadLine();
        }
    }
}