AutoSortingOrderManager / Licence : MIT

AutoSortingOrderManager.cs

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

public class AutoSortingOrderManager : MonoBehaviour
{
    SortedList<int, List<SpriteRenderer>> sortList = new SortedList<int, List<SpriteRenderer>>();
    public int minSortingOrder = 0;
    bool isStart;
    public bool IsStart
    {
        get
        {
            return isStart;
        }
    }
    void Start()
    {
        this.isStart = true;
        SortOrder();
    }
    public void Add(int orderInLayer, SpriteRenderer spriteRenderer)
    {
        ListAdd(orderInLayer, spriteRenderer);
        if (IsStart)
            SortOrder();
    }
    public void Remove(int sortingOrder, SpriteRenderer spriteRenderer)
    {
        List<SpriteRenderer> spriteRendererList;
        if (!sortList.TryGetValue(sortingOrder, out spriteRendererList))
        {
            return;
        }
        spriteRendererList.Remove(spriteRenderer);
    }
    void ListAdd(int sortingOrder, SpriteRenderer spriteRenderer)
    {
        List<SpriteRenderer> spriteRendererList;
        if (!sortList.TryGetValue(sortingOrder, out spriteRendererList))
        {
            spriteRendererList = new List<SpriteRenderer>();
            sortList.Add(sortingOrder, spriteRendererList);
        }
        spriteRendererList.Add(spriteRenderer);
    }
    void SortOrder()
    {
        int i = 0;
        foreach (var temp in sortList)
        {
            List<SpriteRenderer> value = temp.Value;
            foreach (SpriteRenderer spriteRenderer in value)
            {
                spriteRenderer.sortingOrder = i++;
            }
        }
    }
}