LINQ基于childorder对单个列表进行排序

Question

我目前正试图找出一种用LINQ和C#对我的元素进行排序的好方法,但我有点没有这样做.

对于这个问题,我们假设您有以下表格

---TempTable
ID (int)
ParentID (int)
Name (varchar)
SortOrder (int)

ID和ParentID彼此相关,并给我一个自我分层的数据结构.根元素在ID字段中为空.SortOrder只是整个表的一部分,并且基于ParentID,因此共享相同ParentID的元素中包含1,2,3.

让我们进一步假设以下数据:

ID = 1
ParentID = null
Name = Test 1
SortOrder = 1

ID = 2
ParentID = 1
Name = Test 2
SortOrder = 1

ID = 3
ParentID = 1
Name = Test 3
SortOrder = 2

ID = 4
ParentID = 2
Name = Test 4
SortOrder = 1

我想要的平面列表应该具有以下顺序:

Test 1 //root element with sort order 1 = very top
Test 2 //child element of root with sort order 1
Test 4 //child element of test 2 with sort order 1
Test 3 //child element of root with sort order 2

此外,我喜欢获取对象本身,而不仅仅获取一部分信息投入使用select new ...

这是我失败的尝试之一:

from x in EntityModel.TempTables //DbSet<TempTable> by EntityFramework - which already holds all elements
   orderby x.SortOrder
   from y in x.TempTableChildren //Navigation Property by EntityFramework
   orderby y.SortOrder
   select y

在此先感谢您的帮助.

编辑:

具有ParentID的订单可能是有用的,对于给定的TestData,因为ID,ParentID处于完美的顺序但是在真实的实时应用程序中不是这样的,因为它的数据驱动,有人可以删除条目创建一个新条目并将其放入在父母的某些顺序,你会有类似的东西:

ID = 193475037
ParentID = 2
Name = Test 192375937
SortOrder = 25

现在在应用程序中可以移动这个,ParentID和SortOrder会随机变化为:

ID = 193475037
ParentID = 456798424
Name = Test 192375937
SortOrder = 4

为了解释这里的问题是一些代码 - 如果没有1个漂亮的Linq Query我会怎么做但是有2个和一些yield return:

public class LinqTestDemo
{
    Random rand = new Random();
    List<TempTable> list = new List<TempTable>();

    public List<TempTable> GetFlatData()
    {
        list = GetTestData();

        var rootElement = (from x in list
                            where x.ParentID == null
                            orderby x.SortOrder
                            select x).ToList();

        var flatList = OrderChilds(rootElement).ToList();

        foreach (var tempTable in flatList)
        {
            Console.WriteLine(string.Format("ID = {0} - ParentID = {1} - Name = {2} - SortOrder = {3}", tempTable.ID, tempTable.ParentID, tempTable.Name, tempTable.SortOrder));
        }

        return flatList;
    }

    private IEnumerable<TempTable> OrderChilds(List<TempTable> enumerable)
    {
        foreach (var tempTable in enumerable)
        {
            yield return tempTable;

            TempTable table = tempTable;
            var childs = OrderChilds((from x in list
                                        where x.ParentID == table.ID
                                        orderby x.SortOrder
                                        select x).ToList());

            foreach (var child in childs)
            {
                yield return child;
            }
        }
    }

    public List<TempTable> GetTestData()
    {
        var returnValue = new List<TempTable>();
        for (int i = 0; i < 50; i++)
        {
            var tempTable = new TempTable();
            tempTable.ID = i;
            if (i == 0)
                tempTable.ParentID = null;
            else
                tempTable.ParentID = rand.Next(0, i);

            var maxSortOrder = (from x in returnValue
                                where x.ParentID == tempTable.ParentID
                                select (int?)x.SortOrder).Max();

            if (maxSortOrder.HasValue)
                tempTable.SortOrder = maxSortOrder.Value + 1;
            else
                tempTable.SortOrder = 1;

            tempTable.Name = string.Format("Test {0:00}", i);
            returnValue.Add(tempTable);
        }

        return returnValue;
    }

    public class TempTable
    {
        public int ID { get; set; }
        public int? ParentID { get; set; }
        public string Name { get; set; }
        public int SortOrder { get; set; }
    }
}

@Browth-First vs Depth-First Traversal:经过一些阅读后,我会说我想要的结果将是Depth-First Traversal,其中同一级别深度的元素应该由属性SortOrder排序.

Answer 1

  public lEnumerable<TempTable> GetList( int? parentID = null){

     foreach ( var item in Context.TempTables
        .Where( x => x.ParentID == parentID )
        .OrderBy( x=> x.SortOrder)
        .ToList() {

        yield return item;

        foreach( var child in GetList( item.ID))
        {
            yield return child;
        }

     }
  }


  var sortedList = GetList();

它类似于您的方法,但它更小和递归.适用于许多深度级别.我更喜欢调用ToList,因为它会在查询下一个查询之前关闭resultset.

到目前为止,在单个查询中无法执行此操作.

请求单个查询

实体框架将自动填充所有孩子.

 public IEnumerable<TempTable> PrepareList(IEnumerable<TempTable> list){
     list = list.OrderBy( x=> x.SortOrder);
     foreach(var item in list){
         yield return item;
         foreach(var child in PrepareList(item.ChildTempTables)){
             yield return child;
         }
     }
 }

 // since EF will automatically fill each children on fetch
 // all we need is just a top level nodes
 // which we will pass to PrepareList method
 var list = Context.TempTables.ToList().Where(x=> x.ParentID == null);
 var sortedList = PrepareList(list).ToList();

 // it is good to create list at the end if you are going to 
 // iterate it many times and logic will not change.